In an image recording apparatus using an image recording medium which generates a gas when irradiated with a light beam, the gas and the like are prevented from drifting into a space between the image recording medium and a drum, and thus contamination of the back surface of the image recording medium is prevented. The gas is effectively prevented from drifting to the back surface of a plate P by setting a relative positional relationship of an extending direction of each suction groove L, an attaching position of the plate P, and an air blowing direction so that unclosed regions, not closed by the plate P, of suction grooves L formed in a drum surface do not occur downstream in a gas moving direction.