A CTP system is provided, which allows its continuous use even if some of laser diodes located at dispersed sites are in a non-light emitting state due to breakage or the like. In the case where some channels are in the non-light emitting state, channel-by-channel exposure data is generated to describe the way that exposure should be performed by use of specific light-emitting channels that are determined by the locations of non-light emitting channels, while an exposure head is moved also through (a) complementary interval(s) before and/or after a standard interval, the standard interval being the interval the exposure head is moved through in normal mode. Then, the transport unit moves the exposure head through the standard interval and through the complementary interval(s), during which period the exposure controller causes the specific light-emitting channels to emit exposure light according to the channel-by-channel exposure data, thereby forming an exposed area.