A packaging bag having a steam venting function capable of releasing pressure inside a package even when heating cooking is performed by a microwave oven and preventing the inside of the bag from being contaminated and the package using the packaging bag. The packaging bag includes two pieces of front and back main body films having sealant layers which are opposed to each other with the sealant layers facing inward, side seal parts, and a bottom seal part. The front body film is folded in the vicinity of the bottom seal part throughout the entire width of the bag and parallel with the bottom seal part to form a fold-in part. A steam venting port is formed in the fold-in part, and an easily peelable tape covering the steam venting port is disposed on the inside of the fold-in part throughout the width of the bag and parallel with the fold-in part, and then heat-sealed.