Abstract: The invention relates to a U-shaped padlock structure comprising a transverse locking mechanism provided inside the tubular lock body. The locking mechanism consists of a lock cylinder 31, a V-shaped cam 32, a front slide 33, a core rod 34, a resilient element 35, a locating element 36, a center element 37, a rear slide 38, and a short core pin 39 in sequence. The transverse locking mechanism is operated by turning the lock core of the lock cylinder 31 to rotate together with the V-shaped cam 32, which in turn urges the front slide 33, the core rod 34, and the rear slide 38 to move together in a transverse leftward or rightward direction, resulting in a locking or unlocking effect by way of the engagement or disengagement of the core pin with the locking holes formed on the U-shaped shackle.