A surface texture measuring instrument has a pre-load leaf spring (41, 42) for biasing a detector (10) having a skid (14) at a distal end thereof, a pre-load force controller (47) for controlling a pre-load force of the pre-load leaf spring (41, 42), and a stopper (50) for restricting movement of the detector (10) in a biasing direction when a predetermined pre-load force is applied to the detector (10) by the pre-load force controller (47). In conducting a skidless measurement, the detector (10) is locked by applying the predetermined pre-load force to the detector (10) by the pre-load force controller (47). In conducting a skid measurement, the pre-load force less than the predetermined value is applied to the detector (10) by the pre-load force controller (47).