To suppress generation of distortion and cracks due to the difference in thermal expansion by providing a through hole which used not to be linked with a machine parts on a steel parts to generate the martensitic transformation to reduce the difference in temperature between the surface and the inside during the hardening treatment.

In order to prevent distortion or cracks caused by the hardening, a through hole 1a extending in the direction parallel to the axis of compression during the compression is provided in a quench-sintered steel parts 1 to be hardened which has the composition to generate the transformation to the martensitic phase from the austenitic phase through the cooling treatment in addition to a through hole 1b to fit a machine parts such as a shaft. The steel parts 1 contains one or more kinds of additive metal elements which are selected from the group of Ni, Mo, Cu, Mn and Cr, and the total weight ratio of the added metal is ≥1% to <10%, the weight ratio of C is ≥0.4% to <12%, and the balance Fe with inevitable components.