A means for enhancing the yield of a harvesting part of a crop is provided. A yield enhancing agent for a harvesting part selected from the group consisting of seed, fruit, hypocotyl, root and stem in a crop, the yield enhancing agent comprising: 5-aminolevulic acid or a derivative thereof represented by the following formula (1), or a salt thereof; and a gibberellin biosynthesis inhibitor: R2R1NCH2COCH2CH2COR3 (1), wherein R1 and R2 each independently represent a hydrogen atom, an alkyl group, an acyl group, an alkoxycarbonyl group, an aryl group or an aralkyl group; and R3 represents a hydroxyl group, an alkoxy group, an acyloxy group, an alkoxycarbonyloxy group, an aryloxy group, an aralkyloxy group or an amino group, wherein the yield enhancing agent is an agent to be applied at the time when the harvesting part of the crop becomes enlarged.