The present experiments of transient temperature variation and temperature fluctuation were conducted by bead type thermistors in pool boiling without a heat surface. The experimentally obtained conclusion were as follows. (1) The high transient temperature Variatian of 11.64.deg. C for a duration of 0.08 sec and a temperature freguency having a duration of 5.6*10$^{-2}$ sec in a flashing were measured. (2) The highest variation of transient temperature was shown at saturated temperature of 80.deg. C and superheat of 7.9.deg. C. (3) Temperature frequency was found to increase with superheat below 60.deg. C of saturated temperature, but above 60.deg. C it was relative to lower superheat and was found to decrease with higher superheat..