PURPOSE: To provide a movable jaw locking mechanism for stock vice in which movement and fixation of a movable jaw can be quickly and easily performed.

CONSTITUTION: In a stock vice 1 having a fixed jaw 2 and a movable jaw 4 on a vice body 3, a first locking surface part 10 in which a protruding part and a recessed groove extending in the direction crossing the advancing and retreating direction of the movable jaw 4 are repeatedly formed in the advancing and retreating direction of the movable jaw 4 is provided on the reverse surface of the vice body 3, and a locking member 6 having a second locking surface part 19 having a recessed groove and protruding part capable of being engaged with the first locking surface part 10 is provided on the movable jaw 4. A pin 30 and a screw bar 5 are fitted to the locking member 6, and an inclined surface 31 is formed on one end of the pin 30, and brought into contact with an inclined surface 42 formed on the reverse side of the movable jaw 4.