The present invention provides a soluble epoxide hydrolase inhibitor that includes a compound represented by general formula (I) below. In general formula (I): R represents a hydrogen atom, a residue after removing one amino group from an a-amino acid or an amino sugar, a heterocyclic group, an alkyl group having 2 to 8 carbon atoms, or an aryl group; L represents an aliphatic hydrocarbon group having 4 to 10 carbon atoms; X represents a hydroxy group or a carboxy group; and n represents an integer from 0 to 2.