To reduce the amount of deformation of an indenting tool shaft in a push-in testing machine, without causing the handleability of the indentor shaft to be reduced.

The push-in testing machine is provided with the indenting tool shaft 3, where an indentor 1 to be pressed in the surface of a sample S for forming indentation is mounted to its lower part; a loading mechanism part for holding the indentor shaft 3, in such a way as to be freely removable and applying load to the indenting tool shaft 3; and a CPU as a displacement amount measuring means for measuring the amount of displacement of the indenting tool 1 by the application of the load on the indenting tool shaft 3 with the loading mechanism part, when indentation is formed in the sample S by the indenting tool 1. The indentor shaft 3 is provided with a recession part 311, formed in such a way as to be recessed to a prescribed depth from its upper end part; and the bottom surface of the recession part 311 is provided with a displacement amount measurement reference part 32 that serves as a measurement reference for the amount of displacement of the indenting tool 1 by the CPU.