The present invention provides a thickening/foam-promoting agent having thickening/foam-promoting properties and a low odor, and a detergent composition containing the agent. The thickening/foam-promoting agent is composed of the following component (A):(A) a compound represented by the following formula (1): R1O—(PO)n/(EO)m—R2  (1), wherein R1 is a linear alkyl or an alkenyl group having 8 to 10 carbon atoms, PO is a propyleneoxy group, EO is an ethyleneoxy group, an average added molar number n is a number of 1.5 to 3.0, an average added molar number m is a number of 0 to 1.0, and R2 is a hydrogen atom or a methyl group, wherein the content of an alcohol of the formula (1), when n=0, m=0 and R2 is a hydrogen atom, is not more than 3000 ppm, and the detergent composition contains the component (A) and a surfactant (B).