To provide a lock device storable in a stile with a small width by minimizing the depth of the lock case in the square bolt advancing/retreating direction.

This lock device 100 in which a latch for holding a door closed state is formed in a square bolt shape includes: the lock case 25 stored in a stile at a door open/close end; an input member 21 installed in the lock case 25 and rotated by operation members installed at the front and rear of a door; a slide cam plate 37 installed in the lock case 25 reciprocatingly along the stile; a square bolt 15 so installed in the lock case 25 as to advance/retreat from a door opening/closed end surface; a pressing plate part 165 formed on the input member 21 and pushing up the slide cam plate 37; an engagement means 137 for converting the vertical motion of the slide cam plate 37 into the retreat-advance motion of the square bolt 15 and transmitting that motion; and a clutch body 35 engaged with the slide cam plate 37 at the upper end movement position of the slide cam plate 37 to hold the slide cam plate 37 at the upper end movement position.