To provide a novel gelling agent containing a mono-urea derivative. A gelling agent comprising a compound represented by formula [1] (in the formula, R1 represents a C2-20 straight chain or branched chain alkyl group, a C3-20 cyclic alkyl group, or a C12-20 straight chain or branched chain alkenyl group, Ar represents a C6-18 aryl group which is non-substituted or may be substituted with at least one substituent selected from the group consisting of C1-10 alkyl groups, C1-10 alkoxy groups, C6-18 aryloxy groups, a halogen atom, nitro groups, phenyl groups, C2-10 alkylcarbonyl groups, and C7-18 aralkyl groups).
