The stepping motor (10) comprises a rotary shaft (13), a cylindrical stator (2B,3B) including first and second driving coils (2A,3A) disposed along an axial direction of the rotary shaft (13) and energizable with driving currents having different phases, a cylindrical permanent magnet rotor (12) secured to the rotary shaft (13) in a coaxial relationship with the stator (2B,3B) and magnetized in a predetermined pattern, a housing (5,6) to which the stator (2B,3B) is secured and in which the rotor (12) is accommodated for movement in the axial direction of the rotary shaft (13) together with the rotary shaft (13), and fixing means (15) for adjustably fixing the rotor (12) with respect to the housing (5,6) at a position in the axial direction of the rotary shaft (13) at which the detent torque of the stepping motor (10) presents a minimum value. An adjusting method for minimizing a detent torque of such stepping motor (10) and a torque measuring apparatus which is used to put the adjusting method into practice are also disclosed.