PURPOSE: To automatically remove foam reservoir generated in an upper part of an uppermost main bar of a reinforcing bar during foaming by horizontally movably providing an elevator for vertically moving a plurality of auxiliary elevating means having an insert by main elevating means when a lightweight concrete with reinforcing bars is molded, and inserting inserts into slurry.

CONSTITUTION: An elevator 9 mounts rails of a trestle 24 on a support 51 of a moving element 25 horizontally moved by driving means 20. Main elevating means 10 of the elevator 9 vertically moves a connector 16 having a support 52 by a hydraulic cylinder 12 provided at a support frame 54 of a support 15. Auxiliary elevating means 11 are respectively provided at a plurality of inserts 17 to be individually elevated to mount a support 53 at the support 52. The means 11 mounts second elevating means 14 having the inserts 17 at an output driver of first elevating means 13, a plurality sets of the means are provided, and the supports 53 are movably provided on the rails provided on the support 52 to cope with a change in a pitch of main bars 3 in the form by regulating means.