1. An electronic clinical thermometer for predicting an equilibrium temperature based on a temporal change in actual measurement value of a measurement target temperature detected by a temperature detection element, comprising prediction value derivation means for deriving a plurality of prediction values from actual measurement values in accordance with a plurality of prediction equations, selection means for selecting one of the plurality of prediction equations on the basis of the selected prediction equation, and display output means for displaying a prediction value result on the basis of the selected prediction equation.