An optical signal correction apparatus includes a power information generation unit that generates power information indicating power of optical main signal in wavelength band according to optical wavelength multiplexed signal, a power information adjusting unit that generates adjusted power information obtained by adjusting the power information according to the number of the optical main signal included in the wavelength band based on optical signal identifying information which identifies the number of the optical main signal in the wavelength band, a correction amount calculation unit that calculates a tilt amount of the optical wavelength multiplexed signal according to the adjusted power information, and a correction amount for correcting a tilt of the optical wavelength multiplexed signal according to a difference between the calculated tilt amount and a target tilt amount, and an optical signal correction unit that corrects the tilt of the optical wavelength multiplexed signal according to the correction amount.