To precisely determine the strength in an optional position of hardened concrete in a constructing site.

A mechanical anchor-type drawing bar 1 is inserted to a mounting hole 11 with an extended bottom formed in an optional position of concrete 10 after hardening, an extending part piece 31 on the tip of the drawing bar 11 is then extended within the extended hole part 12 of the mounting hole 11, and an adhesive 4 filled in the clearance between the mounting hole 11 and the drawing bar 1 is hardened to fix the drawivng bar 1 in the concrete 10. A reaction is supported by a cylindrical body 8 arranged on a circle concentric to the drawing bar 1 on the surface of the concrete 10 to draw the drawing bar 1, and the compression strength of the concrete is determined by use of the shearing strength when the concrete 10 is conically sheared and broken.