To provide a reversal latch lock enlarging the projecting degree of a latch from a case so as to be surely settled in a receiving seat to secure a lock state even if the thickness of a door and a lock case is thin.

The latch 2 includes a latch part 2a of substantially triangular shape from the front view having a horizontal surface 2b and an inclined surface 2c. The latch part 2a is projected outward from the lock case 1, and a rotating shaft part 2d is formed inside the horizontal surface 2b. A length from the shaft part 2d to the outer end of the horizontal surface 2b is formed to be longer than a height from the shaft part 2d to the upper end of the inclined surface 2c, and an engaging part of a latch piece 3 is formed at the upper part. The latch piece 3 is formed with an engaging surface 3a engaged with the latch 2 outside, and an engaging part of a latch piece spring 6 inside. A latch plate 4 is formed with a fitting engaging part 4b externally fitted to the rotating shaft part 2d of the latch 2 outside of a body, and an engaging part 5 with which the latch piece spring 6 and a latch plate spring 7 are engaged, inside.