Easy-to-open packing bag

An easy-to-open packing bag, comprising:

• a pair of rectangular-shaped packing films, each of which comprises a substrate layer and a thermoplastic resinous layer, said packing films being laminated on each other with surfaces of said thermoplastic resinous layers being opposed to each other;
• a U-shaped peripheral heat-bonding portion being formed on three other sides of said packing films;
• and
• a projected heat-bonding portion, connecting a pair of ends of said peripheral heat-bonding portion and projecting outwardly, formed on said packing films;
• wherein a predetermined region on one side of said packing films is formed as a non-heat-bonding portion;
• wherein at least said projected heat-bonding portion is separably sealed;
• wherein notches are respectively formed on a pair of edges of an external one of the packing films at a position adjacent to one end of said peripheral heat-bonding portion;
• and
• wherein as an operation to separate said packing films at the projected heat-bonding portion from each other proceeds, said external one of said packing films tears from one of said notches to the other of said notches, so that a part of said external one of said packing films can be cut off.