In an information detecting apparatus (1), a speech kind discrimination unit (11) discriminates and classifies an audio signal at an information source into kind (category) such as music or speech, etc. on a predetermined time basis, and a memory unit/recording medium (13) records discrimination information thereof. A discrimination frequency calculating unit (15) calculates, on a predetermined time basis, discrimination frequency every kind at a predetermined time period longer than the time unit. A time period start/end judgment unit (16) is operative so that in the case where discrimination frequency of a certain kind becomes equal to a predetermined threshold value or more for the first time, and the state where the discrimination frequency is the threshold value or more is continued by a predetermined time, start of continuous time period of the kind is detected, and in the case where the discrimination frequency becomes equal to the predetermined threshold value or less for the first time, and the state where the discrimination frequency is the threshold value or less is continued by a predetermined time, end of continuous time period of the kind is detected.