To provide a T section having no welded part and a structure excellent in strength which is suitable for the substitute of a built-up T longitudinal and a manufacturing method of the T section.

By rough rolling a beam blank 5 heated to a prescribed temperature in a heating furnace 6 with a roughing mill 8 consisting of an upper roll and a lower roll, next, rolling the beam blank 5 with an intermediate universal rolling mill 12, an edging rolling mill 14 and a finishing universal rolling mill 18, an I section having an I-shaped cross section is obtained. By rolling the web of the I section in the longitudinal direction, the T section is obtained. In the T section having a T-shaped cross section obtained, the ratio of the web height to the flange width is 2.0-3.5.