The purpose of this paper is to examine a contact stress distribution at the interface of a cylindrical clamped part fastened with a tap bolt to a body which is sufficiently larger than the clamped part. The contact stress distribution is analyzed as a contact problem of two bodies by using the axisymmetric theory of elasticity. The effect of positions of screw thread on the contact stress distribution is clarified in the numerical calculations. The load factor and the ratio of additional axial bolt force to a load are also analyzed. It is found that the contact stress becomes greater near the bolt hole when the position of screw thread is the upper. Experiments to measure the contact stress and the load factor are carried out. The analytical results show a fairly good agreement with the experimental ones. In addition, the contact stress distribution, the load factor and the maximum bolt stress of bolted circular flanged joints with multiple tap bolts are analyzed by using axisymmmetric theory of elasticity. The experiments to measure the load factor and the maximum bolt stress are carried out. A fairly good agreement is seen between the analytical and the experimental results. It is found that the value of the load factor is small and it is less than 0.1.