In a drain socket for a toilet stool includes a vertical pipe including an upper end connected with the discharge port of the toilet stool, an adjustable pipe extending substantially horizontally from the lower end of the vertical pipe and a connecting pipe between the adjustable pipe and a drain of a toilet. The vertical pipe has a bend causing the vertical pipe to have at its lower end an axis displaced longitudinally and rearward of the toilet stool from an axis at the upper end to define an eccentrically curved flow path. The flow path includes a part located near the bend and formed by increasing a transverse dimension of a longitudinal front end thereof with respect to the toilet stool so that the part has such a noncircular cross section in which a front portion of the section has a larger area than a rear portion of the cross section.