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, R1 represents a C1-6 linear or branched alkyl group that may be substituted by a C6-10 aryl group, a C2-6 linear or branched alkenyl group that may be substituted by a C6-10 aryl group, a C2-6 linear or branched alkynyl group that may be substituted by a C6-10 aryl group, or a C6-10 aryl group, R2 represents a hydrogen atom, or a C1-6 linear or branched alkyl group that may be substituted by a C6-10 aryl group, R3 represents a C1-6 linear or branched alkyl group, a C6-10 aryl group, or a halogen atom, and X represents a halogen atom, and multiple R1s may be the same or different].