A part positioning device (41) provided with support pins (48) which support a magnetic tape recording/reproducing device (1), a measuring device (51) which measures the height and inclination of a top end face (3a) of a reel (3) of the recording/reproducing device (1) and turning operation devices (54) which turn adjusting screws (7) which adjust the height and inclination of the reel (3). The turning operation device (54) includes an engaging part (55) which engages/disengages with/from an engagement groove (8) formed vertically in the adjusting screw (7), a turning operation part (57) which is turned by manual operation, and a turning transmission shaft (59) which is bendable to transmit the turning of the turning operation part (57) to the engaging part (55). The engaging part (55) is disposed at a position facing the underside of the adjusting screw (7) and moved vertically with respect to the engagement groove (8) by manually pushing or pulling the turning operation part (57) in the horizontal direction (C, D). The turning operation part (57) is disposed on the front side where the operator performs operation.