Abstract: An ocular structure for observation apparatus includes a first member, a second member and a main body. The first member includes at least one slot and a plurality of first limiting mechanisms. The second member includes at least one slider extending into the slot and a plurality of second limiting mechanisms. The main body includes an ocular lens unit, wherein the first member and the second member are mounted on the main body. The slider is moved in the slot when the first member and the second member are in relative rotation, and the first limiting mechanisms directly or indirectly match the second limiting mechanisms to position the first member with respect to the second member.