In a hearing aid (100), a control device (4) comprises a transmission characteristic calculator (18), a correction characteristic calculator (21), and a correction component (17). The transmission characteristic calculator (18) calculates an at-fitting transmission characteristic Gf (ω) on the basis of correction-use sound data and first sound data produced by collection at an ear canal microphone (10) of correction-use sound outputted from a receiver (3) during fitting. The transmission characteristic calculator (18) calculates an in-usage transmission characteristic Gu (ω) on the basis of correction-use sound data and third sound data produced by collection at the ear canal microphone (10) of correction-use sound outputted from the receiver (3) according to user operation after fitting. The correction characteristic calculator (21) calculates a correction characteristic H (ω) on the basis of the at-fitting transmission characteristic Gf (ω) and the in-usage transmission characteristic Gu (ω). The correction component (17) corrects input sound data that has undergone hearing aid processing by a hearing aid processor (16) on the basis of the correction characteristic H (ω).