A sound amplification apparatus includes one or more microphones that convert collected sound into an audio signal and transmit the audio signal by radio and a sound receiving apparatus that receives the audio signal transmitted from the microphone and amplifies and outputs the sound based on the audio signal. The sound receiving apparatus is configured to perform sound output control in an emergency mode upon receiving an emergency signal transmitted in response to operation of an emergency switch of the microphone. With this configuration, it is possible to perform appropriate sound control in a dangerous situation such as intrusion of a suspicious person.