A vehicle-interior sound-adjustment apparatus configured to be able to suppress an operating sound of an accessory provided in a vehicle interior of a vehicle being heard by an occupant in the vehicle interior, the vehicle-interior sound-adjustment apparatus comprising: a sound output unit configured to be able to output a sound to the vehicle interior; a startup sound generation unit configured to be able to generate a startup sound emitted at time of startup of the vehicle; and a control unit configured to cause the startup sound generated by the startup sound generation unit to be output from the sound output unit, characterized in that: the vehicle-interior sound-adjustment apparatus further comprises a masking sound generation unit configured to be able to generate a masking sound for masking the operating sound of the accessory; the startup sound generation unit is configured to generate a first startup sound composed of a first sound, and a second startup sound composed of a second sound having a higher frequency than the first sound, and the masking sound generated by the masking sound generation unit; the control unit is configured to cause the first startup sound generated by the startup sound generation unit to be output from the sound output unit in a state in which the accessory is set so as not to perform an operation that emits the operating sound, and is configured to cause the second startup sound generated by the startup sound generation unit to be output from the sound output unit in a state in which the accessory is set to perform an operation that emits the operating sound; and the masking sound generation unit is configured to adjust a frequency at a peak of a sound pressure level of the masking sound in accordance with a cumulative number of operations of the accessory. a sound output unit configured to be able to output a sound to the vehicle interior; a startup sound generation unit configured to be able to generate a startup sound emitted at time of startup of the vehicle; and a control unit configured to cause the startup sound generated by the startup sound generation unit to be output from the sound output unit, the vehicle-interior sound-adjustment apparatus further comprises a masking sound generation unit configured to be able to generate a masking sound for masking the operating sound of the accessory; the startup sound generation unit is configured to generate a first startup sound composed of a first sound, and a second startup sound composed of a second sound having a higher frequency than the first sound, and the masking sound generated by the masking sound generation unit; the control unit is configured to cause the first startup sound generated by the startup sound generation unit to be output from the sound output unit in a state in which the accessory is set so as not to perform an operation that emits the operating sound, and is configured to cause the second startup sound generated by the startup sound generation unit to be output from the sound output unit in a state in which the accessory is set to perform an operation that emits the operating sound; and the masking sound generation unit is configured to adjust a frequency at a peak of a sound pressure level of the masking sound in accordance with a cumulative number of operations of the accessory.