Abstract: A method of detecting embrittlement of a heat-resisting steel comprises evaluating the brittleness of the heat-resisting steel on the basis of the repassivation current value obtained by (a) connecting the steel as the anode of an anode polarization curve measuring apparatus wherein an aqueous solution containing an organic acid and an alkylbenzene sulfonic acid or its salt is used as an electrolytic solution; and (b) raising the anode potential from an active region to a passive region and thereafter lowering the anode potential to measure the repassivation current value.