This study was made to clarify the retentive force of a denture retainer, i.e., a cone-type stud and sleeve attachment. In order to measure the wearing effect, an engaging and disengaging cycle test of 1,000 times was performed. The effects of taper angle (cone angle), sleeve height and thrusting force at engaging stud and sleeve on retentive force were also analyzed. 1. The cycle test had little effect on the retentive force (P not equal to 0.41). 2. The retentive force became greater with decrease of taper angle (P less than 0.0001). 3. The effect of the sleeve height on retentive force differed with taper angle (P less than 0.0001). 4. The retentive force became greater with increase of thrusting force (P = 0.0009), and this effect was greater as the taper angle decreased (P less than 0.0001). 5. The contributions of the factors were approximately 38% in taper angle, 30% in thrusting force and 2% in sleeve height. 6. It could be interpreted that we had better use the retainer with taper angle of 6 to 8 degrees, although the retainer with taper angle of 5 degrees could be applicable to the tooth on which the less occlusal force transmitted.