executing signal processing on an input sound signal and producing a first processed sound signal and a second processed sound signal to localize a sound image of the input sound signal in a reference position;

delaying the first processed sound signal by a number of delay times each being an integral multiple of a sampling period of the input sound signal to produce a first set of delayed sound signals, and delaying the second processed sound signal by said number of delay times to produce a second set of delayed sound signals;

selecting a first delayed signal and a second delayed signal from the first set of delayed sound signals depending on the reference position and a target position in which the sound image is to be localized so as to form a first pair of delayed sound signals, and selecting a first delayed signal and a second delayed signal from the second set of delayed sound signals depending on said reference position and said target position so as to form a second pair of delayed sound signals; and

adding the first delayed signal and the second delayed signal from the first pair of delayed sound signals in a first proportion depending on the reference position and the target position so as to produce a first output sound signal having a delay, and adding up the first delayed signal and the second delayed signal from the second pair of delayed sound signals in a second proportion depending on the reference position and the target position so as to produce a second output sound signal having a delay.