An optical disk drive of the type having a fixed optical unit having a light transmitting hole from which a laser beam is emitted, and a movable head having a light receiving hole from which the laser beam is received, wherein the respective outer edges of the light emitting and receiving holes are surrounded by a pair of annular projections. The annular projections are engageable with each other to provide a seal therebetween when the head is displaced toward the fixed optical unit. The annular projections are preferably made of a cushioning material in which instance they also serve as a cushioning or shock-absorbing member.