The present invention is intended to provide an agent fortreating male infertility which is highly effective to maleinfertility, , and having few side effects . To achieve the object ,an agent for treating male infertility comprising .delta.-aminolevulinic acid shown by general formula (1) , its derivative orsalt thereof:R2R1NCH2COCH2CH2COR3 ( 1 )[wherein R1 and R2 independently represent a hydrogen atom, alkylgroup , acyl group , alkoxycarbonyl group , aryl group , or aralkylgroup ； R3 represents a hydroxy group , alkoxy group , acyloxy group ,alkoxycarbonyloxy group , aryloxy group , aralkyloxy group oramino group ]can be used .
