Provided is a method of manufacturing a high quality phosphonocrotonic acid derivative. The present invention is a method of manufacturing a compound represented by the following Formula (3) by reacting a compound represented by the following Formula (1) with a compound represented by the following Formula (2), which comprises a treatment process using an acid or base. [in the formula, R 1 represents a C 1-6 linear or branched alkyl group that may be substituted by a C 6-10 aryl group, a C 2-6 linear or branched alkenyl group that may be substituted by a C 6-10 aryl group, a C 2-6 linear or branched alkynyl group that may be substituted by a C 6-10 aryl group, or a C 6-10 aryl group, R 2 represents a hydrogen atom, or a C 1-6 linear or branched alkyl group that may be substituted by a C 6-10 aryl group, R 3 represents a C 1-6 linear or branched alkyl group, a C 6-10 aryl group, or a halogen atom, and X represents a halogen atom, and multiple R 1 s may be the same or different].
