The estimation of power in Karate-doh is discussed by means of Tameshi-wari for concrete beams. In order to examine the impact forces produced by Karate-doh hand techniques such as Syutoh-uchi and Tettsui-uchi, Tameshi-wari was performed for simply supported concrete beams and also the concrete beams suspended in air. The numerical simulation was also carried using FEM code to understand a mechanism of the impact breaking of the concrete beam by Karate-doh hand techniques. The three modes of bending deformation of the beam was verified to become dominant when it was subjected to the impact by the hand techniques. It is also found that the impact force generated between the hand and the concrete beam is estimated to be beyond 3 kN.