The present invention is to prevent a burr occurs on the inner peripheral surface of the cylindrical portion as to provide a method for forming the through hole and forming apparatus according to a work circumferential wall that high productivity can reduce the processing cost drastically, the workpiece 10, die 20 inserted into the punch 30 is formed so as to be positioned Sikkim as well as projecting from the cores 32 of the support bar shaped in a cantilever on, the through hole 70 on the inner side of the tubular portion 12 in a state facing the inner wall surface of the part to be drilled, and the cores 32 the punch 30 and the circumferential wall portion to be drilled through holes 70 in and at the same time, the work 10 relative pressure movement Sikkim in a direction comprising a punching process in between the die 20 through the through the work hole 72 formed in a portion on the opposite side , the cores of pressurized pin 35 inserted in the workpiece 10 so as to be in contact with the surface formed so as to punch 30 protrudes in the cores and the surface opposite 33, 32 and the punch 30 By putting driving pressure movement with the punch 30 in the peripheral wall 15 from the inside of the tubular portion 12 forms a through hole 70.