To provide an underwear opening capable of keeping the underwear fitted to the body and preventing it from riding up, and also preventing generation of intrusion pressure or oppressive feeling to the body.

This underwear opening A formed of elastic knitted fabric is such that the tightening force toward the hem is gradually weakened. When the knitting direction of the elastic knitted fabric is parallel to the peripheral direction of the piece of underwear, the tightening force is made weak by using higher-gauged peripheral direction rows with relatively thinner elastic warps than those of a base part. When an elastic circular knitted fabric is used for the opening A, the tightening force is made weak by changing elastic yarns into thinner ones, reducing the number of the elastic yarns to be used in a certain part in the peripheral direction area, using low-gauged woven fabric or changing the knit texture.