To attain automation by forming a form in a cylindrical state with a bottom, perforating an air supply hole at the bottom, and feeding compressed air between form and a specimen under test to extrude the specimen.

A specimen under test solidified in a form B is steadily placed together with the form B at the position of a positioning tool 17 on a table 2 with the bottom disposed upside. The mode switching lever 6 of an operation case 4 is operated, compressed air is fed from a compressor 18 to the downward air supply port of a cylinder 5 to lower holding means 12, engaged to be stopped at the upper end of the form B, and a nozzle 13 is engaged with the air supply port of the bottom (b) of the form B. Then, the lever 6 is operated, the compressed air is fed into the form B via an air supply hose 16 and nozzle 13, the part of the air is smoothly branched to the rising air supply port of the cylinder 5 to raise a piston rod 11. Thus, the pressure balance between the cylinder 5 and the form B is suitable held, the specimen is not separated from the table 2, but gradually pushed down while raising the form B.