Side airbag, airbag apparatus, method of making side airbag

A side airbag (101) includes a panel (10) having a first left face (20) and a first right face (30) and folded along a fold line (12) to form a chamber (11), another panel (40) having a second left face (50) and a second right face (60) and folded to form a chamber (41), wherein the second left face (50) has a second left edge part (51) joined to the first left face (20) along a line from a first upper edge part (22) of the first left face (20) to a first lower edge part (23) of the first left face (20) at a position closer to the fold line (12) of the first panel (10) than to a first left edge part (21) of the first left face (20), and the second right face (60) has a second right edge part (61) joined to the first right face (30) along a line from a second upper edge part (32; 34) of the first right face (30) to a second lower edge part (33; 35) of the first right face (30) at a position closer to the fold line (12) of the first panel (10) than to a first right edge part (31) of the first right face (30).