PURPOSE: To eliminate a defect being so-called inconvenience still reanimated a little in the use of a hearing aid by adjusting separately a low frequency range and a high frequency range to adjust an output voice in response to the individuality of the hearing force of the hearing aid user.

CONSTITUTION: A voice received by a reception microphone 1 is converted into an electric signal, the result is inputted to a preamplifier 8, the signal is amplified to a level and the weak portion of the signal is eliminated, the result is inputted to a high frequency range adjusting circuit 10, the amplification factor of the high frequency range signal is adjusted by an adjusting variable resistor 11 adjusting the voltage impressed thereto and then inputted to a low frequency range adjusting circuit 12. The amplification of the low frequency range signal is adjusted by an adjusting variable resistor 13. The electric signal adjusted in this way is inputted to a power amplifier 14 to amplify the level of the entire signal. For example, a speaker 16 outputs voice to the right ear and a speaker 24 outputs voice to the left ear and the electric signal adjusted depending on the hearing force of the right and left ears is listened to with voice reproduction.