The present invention provides a comfortable sock free from tightness in a sole portion. The sock is constructed so that a bottom extension portion 13, in which the number of courses on the side of a sole portion 8 is larger than that on the side of an instep portion 9, is formed between a toe portion 5 and a heel portion 3, and length in the longitudinal direction of the sole portion 8 is larger than that of the instep portion 9.