An image quality alteration unit (21) performs resolution creation processing on a received image signal using adjusted resolution and noise reduction. An magnification alteration unit (31) then enlarges or reduces the received image signal based on the set zoom ratio. A removable substrate (14) having a storage unit (41) is detachably connected to the alteration device (12). The storage unit (41) stores as history information of control commands relative to a switch of the image signal source, a switch of broadcast channel, and alterations of zoom ratio, resolution, and noise reduction. By collecting the removable substrate (14), it is possible to obtain adjustment information on the quality of output (information on the predictive adjustment values of the resolution and noise reduction, and information on the adjusting region thereof) corresponding to the user's preference at each state based on the stored contents in the storage unit (41).