Abstract: An axle pivoting structure of a children's bicycle includes a shaft tube which is provided at both ends thereof with a position confining recess. The axle is provided at both ends thereof with a crank arm having a shaft support hole. The axle is fastened pivotally to the shaft tube by a first shaft support member and a second shaft support member. The first shaft support member is formed of two semicircular members, with each having an annular lip and an insertion protrusion corresponding in location to the position confining recess. The second shaft support member is formed of a circular tubular member having an annular lip and a tapered cell, in conjunction with two semicircular plug members, with each having an annular protruded edge which is received in the tapered cell. The circular tubular member is provided with an insertion protrusion corresponding in location to the position confining recess.