(a) synthesizing a single-stranded cDNA by using a poly(A) RNA as a template, wherein a single-stranded cDNA bearing a tag substance at the 5′-end side relative to the single-stranded cDNA is synthesized;

(b) synthesizing a double-stranded cDNA by using the single-stranded cDNA synthesized in the step (a) as a template, wherein a double-stranded cDNA bearing a tag substance at the 3′-end side relative to the double-stranded cDNA is obtained;

(c) cleaving the double-stranded cDNA obtained in the step (b) with a first restriction enzyme X;

(d) recovering a fragment bearing the tag substance from fragments obtained in the step (c) by using a substance having a high affinity for the tag substance;

(e) ligating an adaptor X containing a sequence complementary to the sequence of the cleavage site and a sequence complementary to the sequence of a primer X to the cleavage site of the fragment generated by the first restriction enzyme X as recovered in the step (d), to obtain a fragment ligated with the adaptor X at the 5′-end side relative to the double-stranded cDNA;

(f) cleaving the fragment recovered in the step (e) with a second restriction enzyme Y that does not cleave the adaptor X;

(g) removing a fragment bearing the tag substance from the fragments obtained in the step (f) by using a substance having a high affinity for the tag substance, to recover a fragment containing the cleavage site generated by the second restriction enzyme Y at the 3′-end side relative to the double-stranded cDNA;

(h) ligating an adaptor Y containing a sequence complementary to the sequence of the cleavage site and a sequence complementary to the sequence of a primer Y to the cleavage site of the fragment generated by the second restriction enzyme Y as recovered in the step (g), to obtain a fragment of a double-stranded sequence ligated with the adaptor Y at the 3′-end side relative to the double-stranded cDNA;

(i) performing a PCR reaction with the fragment of the double-stranded sequence obtained in the step (h) as a template by using a primer set composed of a primer X containing a sequence complementary to the sequence of the adaptor X, which has the sequence of 2 bases N₁N₂ at the 3′-end side relative to the primer X, wherein N₁and N₂ may be identical or different bases that are selected from the group consisting of adenine, thymine, guanine and cytosine, and a primer Y containing a sequence complementary to the sequence of the adaptor Y, which has the sequence of 2 bases N₃N₄ at the 3′-end side relative to the primer Y, wherein N₃and N₄ may be identical or different bases that are selected from the group consisting of adenine, thymine, guanine and cytosine; and

(j) subjecting the obtained PCR product to electrophoresis and detecting the migration distance and peaks to prepare a gene expression profile,

wherein, in the step (i), the annealing of the primer X and the primer Y to the adaptor X and the adaptor Y respectively is carried out in the temperature range of TmMAX+6° C. to TmMAX+14° C. of the primer, wherein Tm is calculated by the formula: Tm(° C.)=2×(A+T)+4×(G+C) wherein (A+T) is the sum of the numbers of adenine (A) and thymine (T) residues comprising a primer and (G+C) is the sum of the numbers of cytosine (C) and guanine (G) residues comprising a primer;

wherein, in the step (i), 256 different primer sets composed of 16 different primers X and 16 different primers Y in combination are used as primer set; and

wherein, in the step (i), the primer X is 5′-ACATGACACTCGGTTCGGN₁N₂-3′,

wherein N₁N₂ is CC, CT, CG, CA, TC, TT, TA, TG, AC, AA, AG, AT, GT, GC, GA, or GG; and the primer Y is 5′-ATACTGCGGGCGTCCTAAN₃N₄-3′,

wherein N₃N₄ is CC, CT, CG, CA, TC, TT, TA, TG, AC, AA, AG, AT, GT, GC, GA, or GG.