A module attachment device includes: a first module that includes a first casing and a first moving member, the first moving member being configured such that when a first end is pushed, a second end protrudes from the first casing; and a second module that is engaged with a mounting surface, and includes a second moving member that is disposed at a position where the second moving member is capable of pushing the first end of the first moving member, wherein in response to the first end of the first moving member being pushed by the second moving member, the second end of the first moving member protruding from the first casing comes into engagement with the mounting surface.