A speaker determination device determines a polarity of a speaker connected to output terminals. Test sound is outputted to an acoustic space via the connected speaker and is collected by a microphone. A reference signal is generated based on the test signal. A polarity determining unit compares predetermined frequency range components of the microphone signal obtained by the microphone and the reference signal, and determines the polarity of the speaker, i.e., whether the speaker is connected in positive phase or in negative phase.