A chucking pulley clamps and chucks a recording medium in coaction with a disk table. The chucking pulley has a rotary slide knob and is rotatably supported on a support arm. The support arm has first and second lifting/lowering pins. A holder is mounted on the support arm for pressing the chucking pulley toward the disk table while in contact with an end of the rotary slide knob when the recording medium is in rotation. A spring is resiliently held against the first lifting/lowering pins. Moving members move the chucking pulley toward and away from the disk table. The moving members have retainers for retaining the first lifting/lowering pins in an acting position when the recording medium is chucked. The first lifting/lowering pins retained in the acting position deform the spring to bias the support arm and the holder toward the disk table.