Rectangular bag

The utility model discloses a rectangular bag which comprises a bag body and a strap, wherein the bag body comprises a top side edge sheet and a bottom side edge sheet which are symmetrical to each other up and down, and a left side edge sheet and a right side edge sheet which are symmetrical to each other left and right; a first combining piece is arranged on the left side edge sheet; the shortest distance between the first combining piece and the top side edge sheet is a first distance; a second combining piece is arranged on the right side edge sheet; the shortest distance between the second combining piece and the top side edge sheet is a second distance; the first distance is smaller than the second distance; two ends of the strap are connected with the first combining piece and the second combining piece, respectively. Space defined by the strap is large, so that a user can stretch the body in a comfortable way when carrying the rectangular bag on the back.