The object of the present invention is to provide a new organic phosphorus ligand that can efficiently promote cross-coupling reaction to obtain the target substance at high yield, as well as a method of manufacturing such ligand whose steric characteristics and electronic characteristics can be fine-tuned and which can be used to cause cross-coupling reaction at high yield. As a means for achieving the aforementioned object, a phosphine compound expressed by General Formula (1) below is provided. (In the formula, R1 and R2 are each independently a secondary alkyl group, tertiary alkyl group, or cycloalkyl group, while R3 and R4 are each independently a hydrogen, aliphatic group, heteroaliphatic group, aromatic group, alicyclic group, or heterocyclic group. Note that R3 and R4 have no phosphorus atom and that R3 and R4 are not both hydrogen at the same time).