The present invention provides a sound signal processing device that precisely detects various kinds of noises and that does not block output of voice signals even when detecting noise during the output of the voice signals. The sound signal processing device according to the present invention comprises: an input part 10; an input signal determination part 20 that determines whether an input signal from the input part is present; a noise detection part 30 that detects noise included in the input signal from the input part; an output part 80 that outputs the input signal as an output signal; an output switching part 52 that performs switching between an output state in which the output part outputs the output signal and a non-output state in which the output part does not output the output signal; and a control part 60 that controls the switching performed by the output switching part. The control with the control part for switching includes first control that controls the switching based on a determination result r1 from the input signal determination part and a detection result r2 from the noise detection part, and second control that controls the switching based on the determination result from the input signal determination part. One of the first control and the second control is selected based on a state of the output switching part.