Abstract: A tube for a bicycle has a body, an indented portion, and a machined hole. The indented portion is radially recessed in the body and has an outer bottom surface, an outer annular surface, and a first round corner being a curved surface smoothly connecting an outer tube surface of the body and the outer annular surface. The machined hole is formed through the outer bottom surface of the indented portion and has an area being less than an area of the outer bottom surface. The indented portion formed around the machined hole distributes stress to prevent cracking occurring from an edge of the machined hole. The structural strength of the tube is increased under a same total weight.