To provide cozy and sanitary men's underwear trunks by solving unfavorable wearing feeling of conventional men's underwear trunks.

The men's underwear trunks comprise conventional men's underwear trunks and an inner fabric provided at the inside of the trunks. The inner fabric is made of highly stretchable fabric, formed by exchanging the fabrics to be sewn so as to three-dimensionally fit the body from the front waist to the back waist along the hip line while covering the belly part, and provided with an opening part having a cylindrical rise-up part for passing the mail genital organ therethrough. Such a structure prevents the mail genital organ from coming in contact with the skin of the femoral region so as to improve air permeability. Use of the stretchable fabric and the three-dimensionally exchanging sewing technique prevent the mail genital organ from getting off the body when the wearer takes exercise so as to make the trunks fit to his body.