To simply rationally constitute a holding member provided on the back of a seat back.

A width-directionally long holding band 10 (holding member) provided on the back (backboard 2B) of a seat back 2 holds a stored entity P inserted from the height direction into a holding space N between the holding band 10 and the back of the seat back 2 by elastically pushing the stored entity P to the back of the backboard 2B. The whole of the holding band 10 is integrally formed by a stretchy material. The stored entity P is held by the holding band 10, whose both ends 12 and 13 in the longitudinally wide direction are respectively inserted into and attached onto the back of the backboard 2B under the elastically attached condition.