A sheet-material transporting device includes: plural first endless-belts; a driving-member around which the first endless-belts are trained to circulate; a first driven-member around which the first endless-belts are trained, being slave-rotated; a supporting-member provided at an inner-peripheral-side of the first endless-belts; a second endless-belt provided between the first endless-belts, trained around the driving-member and circulating; a second driven-member provided between the first driven-member and the driving-member, around which the second endless-belt is trained at an opening portion provided in the supporting-member, being slave-rotated; and a detecting-member detecting a sheet-material, the supporting-member including a downstream-side-supporting-member disposed at a downstream-side having a concave-portion formed in an end portion, and an upstream-side-supporting-member disposed at an upstream-side and that is set against the end portion of the downstream-side-supporting-member such that the concave portion forms the opening portion, and a tension-imparting section imparting tension to the second endless-belt being provided at the downstream-side-supporting-member.