A wrist mechanism of an industrial robot comprises: spline teeth (2A) formed in the outer circumference of the end portion of a bending drive shaft (2) which is provided inside of an arm (1); spline grooves (2B) which are formed in the inner circumference of a first bevel gar (21) and are engaged with the spline teeth (2A); spline teeth (3A) formed in the outer circumference of the end portion of a revolving drive shaft (3); a hollow cylindrical intermediate shaft (30) having one end portion in the inner circumference of which spline grooves (3B), which are engaged with the spline teeth (3A), are formed, and the other end portion to the outer circumference of which a second bevel gear (31) is secured; a bearing (301) through which the one end portion of the intermediate shaft (30) is supported on the first bevel gear (21); and bearings (22 and 24) through which the other end portion of the intermediate shaft (30) is supported on a stationary gear box (45).