Bag

A bag comprising:

• a bag body provided with a back plate portion and a storage space for storing items;
• a shoulder slinging portion including a backrest portion corresponding to the back plate portion and a shoulder strap connected to the backrest portion;
• and
• a first coupling portion connecting the back plate portion and the backrest portion in a height-adjustable manner,
• wherein the first coupling portion includes:
• a first body coupling portion coupled to the back plate portion;
• and a backrest coupling portion coupled to the backrest portion and
• the first body coupling portion includes a plurality of coupling areas to which the backrest coupling portion is coupled and provided at different heights,
• wherein the backrest coupling portion includes:
• a first fixture provided in an outside direction of the backrest portion;
• a second fixture provided in a direction of the back plate portion and provided with a circular protruding portion provided in the direction of the back plate portion, and
• a rotational coupling body coupled to the circular protruding portion.