PURPOSE: To make it possible to properly detect pitch for a voice which contains the original pitch component and a pitch component twice as large as it almost to the same extent and to prevent a synthesized sound from deteriorating in quality by judging the pitch of a current block being twice as large as the original pitch when specific conditions are met.

CONSTITUTION: It is judged that the pitch P of the current block is twice as large as the original pitch when at least one of the condition, that is., the pitch P of the current block P is more than twice as large as the typical pitch and the block mean level is larger than a specific threshold value, and the typical pitch is larger than the typical pitch of the last block and the pitch P is larger than the specific threshold value, etc. Namely, it is judged whether or not a value is a half as large as the pitch extracted by a pitch extraction part 13 at the time of voice pitch extraction should be used. According to the judgement result, a P/2 selection part 26 sends pitch data P from a high-precision pitch search part 16 to an encoding part 21 as they are or after halving them.