A driving belt for stepless speed variation capable of smoothly traveling and accomplishing power transmission with high efficiency. The driving belt includes an endless metal strip consisting of a plurality of first metal strip elements and a second metal strip element formed into a length larger than the first metal strip elements, a plurality of blocks each provided at a center of an upper portion thereof with a groove through which the endless belt is fittedly inserted and having both side surfaces in a direction of advance of the driving belt curved, and a plurality of pins each arranged so as to extend across the groove of the block. The second metal strip element is formed into a corrugated shape, resulting in exhibiting elastic force and the both side surfaces each are formed so as to have a center of curvature defined at an intermediate position of a depth of the groove, so that the blocks adjacent to each other may abut against each other near the metal strip.