To manufacture a concrete product in which a reinforcing-bar can be arranged at an upper side within a form.

A reinforcing-bar interval holder body 1 is mounted in an intersection of reinforcing-bars G disposed within a form W and lattice-shaped in a planar view. After the reinforcing-bars G lattice-shaped in the planar view are horizontally disposed within the form W by mounting a hanger part 11 which is formed while protruding upwards from the main body 1, on a support pole X horizontally bridging, in a freely removable manner, between upper end portions Wa and Wb opposing via an upper opening W1 of the form W, concrete is installed within the form W. After the concrete is cured and solidified, the hanger part 11 protruding from a concrete product is cut, the support pole X is removed from the form W, and form removal is performed.