To improve the total quality of a speech by intermittently sending information regarding background noise at need once an inactive speech frame is detected by including a step for generating an inactive speech bit stream by using an arrival speech signal encoded by an inactive speech encoder unit.

This device includes the step for generating the inactive speech bit stream by using the arrival speech signal 105 encoded by the inactive speech encoder unit 115 when a decision on a frame speech indicates an inactive speech. When the decision on the frame speech indicates the inactive speech, the inactive speech bit stream is transmitted only condition that predetermined comparison reference is met and in this case, an inactive speech decoder unit 165 is called to generate a restored speech signal. Further, when the inactive bit stream is received by a speech decoder unit 155, the inactive speech decoder unit 165 is updated, but when not, inactive speech information which is received before is used.