An image forming device includes a scanner swingable between a closed position to close an upper side of a catch tray of a printer and an opened position to open the upper side of the catch tray, a positioning mechanism having a protruding section formed at one of the printer and the scanner and a recessed section formed at the other such that the protruding section is fitted thereinto in the closed position, and a lock mechanism configured with an engagement hole formed at one of the protruding section and the recessed section and an engagement portion formed at the other so as to hold the closed position by engagement therebetween. When the scanner is swung to the closed position, a contact portion of the protruding section contacts a contact portion of the recessed section before the engagement portion contacts the engagement hole or a region around the engagement hole.