A tray locking device adapted to an optical disc drive for locking and releasing a tray is provided. The optical disc drive has an optical head connected to a lead screw and driven to move by the lead screw. The tray locking device includes a pushing member driven to move by the lead screw, a latching hook for locking and releasing a protruding pin, and a transmission assembly configured between the pushing member and the latching hook. The transmission assembly includes a first rod and a second rod movably configured in the tray. The first rod has a first driving portion, and the second rod has a second driving portion. When the transmission assembly is located at an initial position, the first driving portion is located on a moving path of the pushing member, while the second driving portion is not located on the moving path of the pushing member.