A predictive-type electronic clinical thermometer comprises a temperature sensing unit, a measuring unit for measuring elapsed time from the start of measurement and an arithmetic unit. The arithmetic unit performs a predictive operation in order to obtain a corrective value utilizing one selected prediction function at one time from among a plurality of prediction functions in which elapsed measurement time is a variable, each function defining a temperature change up to a final temperature. The arithmetic unit calculates the equilibrium temperature based upon the obtained corrective value and the sensed body temperature. In a case where an unstable temperature rise curve exhibits a transition not covered by the group of standard curves which are defined by the predictive functions, the prediction operation is suspended immediately and the actually measured temperature value is displayed at such time.