Abstract: A multifunctional bag structure includes a main bag which is a foldable bag structure and has a contractible strap disposed at the connection position of a front wall and two sidewalls for selectively fixing a rear fixing section corresponding to a rear wall or a front fixing section corresponding to a sidewall to fit a contracted or expanded form of the main bag. At least one fixed strap is fixed to an end of the rear wall, and at least a binding ring is disposed on another end. A cart has a wheel at both sides at the rear end of a support base, and two pulling rods are extended upward from the cart, and a handle is installed at the top of the pulling rod, so that the movable end of the fixed strap passes over the two pulling rods to another end of a binding ring and is folded in a reverse direction to connect the fixed strap. The main bag and the cart are integrated as a whole.

Abstract: This invention discloses a backpack, which comprises a bag having an accommodating space therein; a latch device disposed on both sides of the bag for opening or closing the bag; two shoulder straps respectively coupled to the upper and lower sections of both sides of the rear of the bag for carrying the bag on a user's back; two speakers, built in and exposed from both sides of the front of the bag, and a signal line for connecting the two speakers, and one of the speakers having a signal input line and a plug; thereby the two speakers are capable of producing sound by connecting the plug with a signal output socket of a portable player.