A rotary device includes a rotatable member and a limiting member. The rotatable member includes a positioning mechanism, the positioning mechanism includes a stopping member and a positioning member. When the rotatable member rotates along a first rotation direction to make the limiting member abut against the positioning member, the positioning member is pushed by the limiting member to move away from the stopping portion and rotate relative to the stopping member, so that the positioning member to passes through the limiting member. When the rotatable member rotates along a second rotation direction opposite to the first rotation direction to make the limiting member abut against the positioning member, the positioning member is pushed by the limiting member to move close to the stopping portion, so that the positioning member is stopped between the limiting member and the stopping portion, to position the rotatable member.