Abstract: A packing bag comprises a flat main body made of a synthetic resin film or sheet, sleeves formed around a top end of the main body and each divided into upper and lower chambers, and drawstrings each inserted in the respective chambers of each sleeve. A plurality of engaging portions in the form of knurled indentations are formed between the upper and lower chambers and below the lower chambers so that an increased friction and a reduced stiffness are imparted to the sleeve, in such manner that after the top end portions are gathered by pulling the drawstrings in opposite directions, the increased friction and reduced stiffness prevent the top end from opening unintentionally due to a possible resilient restoration of its ungathered state.