Provided is an enhancing agent for cancer heat therapy that is not combined with photodynamic therapy. Using a 5-aminolevulinic acid represented by formula (1) R2R1NCH2COCH2CH2COR3 (1) [in the formula, R1 and R2 each independently represent a hydrogen atom, alkyl group, acyl group, alkoxycarbonyl group, aryl group or aralkyl group; and R3 represents a hydroxyl group, alkoxy group, acyloxy group, alkoxycarbonyloxy group, aryloxy group, aralkyloxy group or amino group] or salt thereof as a cancer heat therapy-enhancing agent allows cancer therapy that is not combined with photodynamic therapy.