To prevent the occurrence of tear by improving tensile strength in the widthwise direction while improving the flexibility of a flat belt by keeping the flexural strength in the longitudinal direction of the belt to be proper and to improve connection work properties.

In the structure for connecting the flat belts 1 together by the ends 4 and 5 in the longitudinal direction, both ends are formed in the shape of saw teeth in the thickness direction, engaged with each other, and welded together by a thermoplastic resin. The resin is welded to the surface and/or the back of engagement 8, or to the intermediate layer of the engagement part to form a reinforcing layer 9. A nonwoven fabric 10 is fixed to the reinforcing layer with fibers oriented in the widthwise direction of the belt.