A sheet conveying apparatus includes an apparatus main body, a sheet cassette, a mounting portion and a conveying unit. The sheet cassette is mounted into the apparatus main body. The conveying unit is arranged above the sheet cassette in the apparatus main body. The conveying unit includes a conveyance path, an upper guide unit, a lower guide unit and a locking mechanism. The upper guide unit defines an upper surface part of the conveyance path. The lower guide unit defines a lower surface part of the conveyance path and enters the mounting portion to open the conveyance path. The locking mechanism locks the lower guide unit to the upper guide unit. The lower guide unit includes a projecting piece. The sheet cassette includes a push-up portion. The push-up portion pushes up the projecting piece when the sheet cassette is mounted into the mounting portion.