This invention concerns an infusion bag, especially for tea, which has a top part with folded down corners and a middle part folded over it, to which a string with two free ends is attached that goes from one side of the top part through a hole in the folded down parts forming a loop on the other side of the top part and comes back, whereby the two free ends are drawn up through the loop laid over the top edge of the infusion bag and pulled to form a knot. The solution in the invention is characterized by the fact that two holes are made in the top part at a lateral distance next to one another, on the left and right of the longitudinal axis of the bag; each hole goes through a folded down corner and the middle of the top part; by the fact that the string forms a loop and one end goes through one hole and the other end through the second hole; by the fact that the loop is laid over the top edge of the infusion bag, and both ends of the string go up through the loop to form a double knot. The invention also concerns a method of closing an infusion bag.