A backpack with a torso length adjustment mechanism is provided. The backpack includes a holder fixedly connected to a bag, a mesh back support having a back mesh contactable to the back of the user and a supporting element for spacedly supporting the back mesh on the holder. The backpack includes a shoulder strap length adjusting mechanism having a force transmitting element for transmitting a force from the holder to the shoulder straps of the backpack. The force transmitting element is lockably movable on the holder between a first position in which a size of the shoulder straps is the largest and a second position in which the size of the shoulder straps is the smallest. The shoulder strap length adjusting mechanism includes a locking mechanism at the holder for releasably locking a movement of the force transmitting element.