A disk loading mechanism has a turntable. A turntable 36 itself is fixed in external dimensions of a brushless spindle motor, and a chucking face relevant to a disk 11 is precisely placed on a turntable base 46 with a predetermined height. On the turntable base 46, columns 47 are embedded in three directions on a circumference which surrounds the outer periphery of the turntable 36. A column tip end stepped portion 47b and a disk placement face 36a of the turntable 36 are precisely constructed in predetermined dimensions. When the column tip end stepped portion 47b abuts against a bottom face (a reference face L) of a drive board 15, a relative position between the disk placement face 36a of the turntable 36 and a pickup constructed while the bottom face of the drive board 15 is defined as a reference is precisely determined.