A locking mechanism in a printing apparatus includes a slide member inside an outer casing at a position corresponding to an opening in an outer casing of the printing apparatus, the slide member being configured to be moved in a slide direction to switch a state of an access cover between a locked state and an unlocked state, and a restriction portion configured to be moved in the slide direction together with the slide member, in which when the slide member is in a lock position, the restriction portion protrudes from the opening and the movement in the slide direction is regulated, when the slide member is in an unlock position, the restriction portion is retracted inside the opening and the movement in the slide direction is permitted, and the restriction portion includes an operation portion configured to move the slide member between the lock position and the unlock position.