A motor driving device capable of being more easily installed at a mounting member. The motor driving device includes a mounting member including a mounting hole; a fan unit configured to be fixed to the mounting member, the fan unit including a lid disposed to cover the mounting hole; a restricting member configured to restrict movement of the lid in an away direction from the mounting member by sandwiching the lid between the restricting member and the mounting member; and a guide mechanism configured to guide an operation of the restricting member moving along the lid from a non-restricting position where movement of the lid in the away direction is allowed to a restricting position where movement of the lid in the away direction is restricted.