In order to confirm the theoretical results developed in the preceding reports, the author made measurements of the escapement error.The experimental method devised by him makes possible to record both the amplitude and the period of the balance oscillation optically, and especially it has such large magnification of time that, in the case of the free oscillation without the escapement, the small variation of the period, in accordance with the amplitude damped by the friction, can be measured. The difference of the period measured with and without the escapement at the same amplitude gives the escapement error corresponding to that amplitude.Measurements were made in four cases of one pin-lever escapement and two lever escapements.The calculated values by the theories were compared with the corresponding measured values.The results showed that the theory of part I has fairly good qualitative applicability and that of part II quantitative.