An under body may include a side sill inside front panel bent similar to the side sill inside panel to connect a front end portion of the side sill inside panel with a dash panel to be bonded to each other; a front side member connecting member connected with a bottom surface of the dash panel and a rear end portion of a front side member while being bonded to an inside surface of the side sill inside front panel; a side sill inside rear panel configured to connect a rear end portion of the side sill inside panel with a rear side member to be bonded to each other; and a rear side member connecting member configured to connect a bottom end portion of the side sill inside rear panel with a front inside surface of a rear side member to be bonded to each other.