To enable a concrete material to be supplied in uniform density to a form.

A notch 40c is formed in the lower end part of a base end wall 40b which becomes a rear end during backward movement, in the side wall of a feeder hopper 40. At the same time, a gate member 60 is arranged under such a state that the notch 40c is opened and closed. The position of the gate member 60 is changed to a form 1 by actuating a lifting cylinder when the feeder hopper 40 is moved backward.