Abstract: An easy-to-open synthetic resin bag comprises (a) a bag body substantially consisting of a pair of laminated walls made of synthetic resin films, the peripheries of the laminated walls being heat-sealed to form a sealed border region while defining an unsealed storing space within the sealed border region, (b) a tear string which is heat sealed along an imaginary opening line on the inside of one of the laminated walls, the tear string having both ends thereof heat sealed in a sandwiched condition on the corresponding portion of the sealed border region, (c) a pulling tab formed by cutting a part of one side portion of the sealed border region which corresponds to one end of the tear string, the pulling tab being tearable from the bag body integrally with the tear string, and (d) a tear string retaining portion comprising a transverse opening which is formed by cutting off a part of the other side portion of the sealed border region and a pair of inside and outside heat sealed portions which are located at bo