To realize both transmission efficiency and low delay performance of two-way communication.

A speech encoding device is provided with a 1st encoding part 101 which uses a 1st speech encoding system having small encoding delay and a 2nd encoding part 103 which uses a 2nd encoding system having larger encoding delay and a lower encoding bit rate than those of the 1st speech encoding system. An encoding selection part 105 detects the degree of two-way of speech communication by using a transmission-side input speech signal and a reception-side decoded speech signal and properly selects one of the 1st encoding part 101 and 2nd encoding part 103 as an encoding means of encoding the transmission-side input speech signal on the basis of the detected degree of two-way of speech communication.

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