To provide a means for reinforcing the firmness of foam of a detergent and improving the resistance of the foam to a defoamer such as a silicone.

The detergent is obtained by including (1) one or two or more kinds of polyalkylene glycols having 10,000-400,000 average molecular weight and (2) one or two or more kinds of anionic surfactants. Polyethylene glycol is especially preferably exemplified as the polyalkylene glycols. A form containing a fatty acid potassium as a main detergent in an amount of preferably ≥80 wt.%, more preferably ≥90 wt.% based on the whole anionic surfactant is especially preferred as the anionic surfactants.