Abstract: A mechanism for loading compact discs or similar rotary discs, in which two guide arms are rotatably mounted on a base plate symmetrically with respect to its center line and a disc detect arm is rotatably mounted on each guide arm. Each guide arm has a large-diametered disc holding portion for holding a large-diametered disc and a small-diametered disc holding portion for holding a small-diametered disc. Each guide arm is being applied a moment which reverses its direction when the guide arm passes a predetermined rotational angular position of the guide arm. The disc detect arm is being applied a moment in a direction in which a projection provided at its one end enters into the large-diametered disc holding portion and the other end of the disc detect arm slides in an L-shaped guide slot made in the base plate, thereby limiting the rotational movement of the disc detect arm and the rotational movement of the guide arm.