[en] In STP-3(M) reversed-field pinch plasma, the bursts of soft X-rays are periodically observed in association with the toroidal flux regeneration (dynamo action) using surface barrier diode (SBD). The soft X-ray bursts result from high energy electrons colliding with the surface of metal liner and limiters. The energy of colliding electrons analyzed by the absorber method assuming a monochromatic distribution, is found to have a distribution of 2 ∼ 8 keV. The energy of 8 keV is observed at about 100 μs before the termination of the plasma current. The mechanisms of the acceleration and the anomalous diffusion for these high-energy electrons are discussed. (author)