The present invention is provided with a counter-pressure apparatus, comprising; a counter-pressure cylinder installed to be fixed on the ground on one side of the lower part of a pipe transfer unit to exert a force in an opposite direction to a hydrostatic pressure cylinder; a first chain with one end combined to a piston rod of the counter-pressure cylinder and the other end combined to one side of a rotary plate mounted on the lower part of a rotating shaft of a bending unit; and a second chain with one end fixed and combined to a part on one side of the piston rod of the counter-pressure cylinder and the other end combined to the other side of the rotary plate away from a combination point of the first chain by a certain distance. The invention provides a pipe bending apparatus wherein a working radius of the hydrostatic pressure cylinder working for the rotary plate of the bending unit can be changed depending on the pipes, which are work objects, while a working radius of the counter-pressure cylinder acting for the rotary plate of the bending unit maintains a fixed value.