An undergarment for men is formed with multiple layers of fabric materials attached together. A first fabric piece (10) is formed in a brief shape to have a front part (10c), a rear part (10d), a pair of side parts (10e) extending between the front and rear parts (10c, 10d), and a bottom part (10f) extending between a lower portion of the front part (10c) and a lower portion of the rear part (10e), the front part (10c) having a first elastic thread line (14) attached by stitching or sewing to a central area of the front, bottom, and rear parts (10c, 10f, 10e) to exert a suitable elastic force a genitalia region of the wearer. A second fabric piece (20) is attached externally to the first fabric piece (10), wherein the second fabric piece has a belt-like shape extending in a circumferential direction and covering a substantial portion of the first fabric piece (10) but not covering a central portion of the front part of the first fabric piece. A third fabric piece (30) is attached externally to the first and second fabric pieces (10, 20), wherein the third fabric piece is formed in a partial brief configuration having a front part, a rear part, a pair of side parts extending between the front and rear parts, and a bottom part extending from a lower portion of the front part and having a free end, in a shape such that, when attached to the first and second fabric pieces, the front and side parts cover substantially an entire area of the front and side parts of the first fabric piece, respectively, the rear part covers an upper portion of the rear part of the first fabric piece, and the bottom part covers substantially an entire area of the bottom part of the first fabric piece. The third fabric piece (30) preferably includes a second elastic thread line (32) attached by stitching or sewing to a central area of the front part of the third fabric piece.