A medium support unit (2) include a support surface (7) that can support a medium, a depressed portion (11) in which a part of the medium supported by the support surface (7) can be depressed with respect to the support surface (7), and an adjustment unit (8) which can change a size of the depressed portion (11) by changing a state of a first area in the depressed portion (11). By such a configuration, it is possible to suppress a rise of the medium supported by the support surface (7) according to size and shape of a thick part of the medium including the thick part.