A package for a microwave oven configured to hermetically seal and store a content, comprising a film-shaped lid material, and a container (20C, 20D, 20E) for the microwave oven configured to be hermetically sealed by the film-shaped lid material, wherein the container (20C, 20D, 20E), comprises: a concave main body capable of containing a content therein and having an opening, an annularly flanged portion formed at the opening in an upper end of the concave main body, and a rib-shaped thermal fusion portion (40, 40B) formed over a whole circumference of a top surface of the flanged portion configured to be thermally fused to the film-shaped lid material for closing the opening, wherein the thermal fusion portion (40, 40B) is provided with first and second opening portions that are approximately V-shaped such that they project from the opening side toward an outer periphery of the flanged portion in a plan view, wherein each of the opening portions has an end portion located at the outer periphery side and a pair of end portions located adjacent to the opening and is adapted to allow the lid material to be easily separated or removed from the opening portion beginning by the end portion located at the outer periphery side toward the end portions located adjacent the opening, when an edge portion of the lid material is grasp and lifted by hand; a vapor discharge portion that is approximately V-shaped such that it projects from the outer periphery side toward the opening side in a plan view, wherein the vapor discharge portion has an end portion located at the opening side and is adapted to allow automatically peeling of the lid material from the end portion, when the inner pressure of the container increases due to heating; and an annular portion formed along an annular reference line, which is similar to a shape of an inner periphery of the opening, except for the first and second opening portions and the vapor discharge portion, wherein a pair of end portions of the vapor discharge portion located at the outer periphery side is located closer to the outer periphery than the reference line in a cross-and-width direction of the flanged portion, and wherein each of the pair of end portions is connected through an inclined portion to an end portion of the annular portion located at both sides of the vapor discharged portion; wherein the annular portion is disposed at a location less than 50% of a width of the flanged portion from the opening; characterized in that, the V-shaped first and second opening portions are formed adjacent to either side of the V-shaped vapor discharge portion as to form a multifunctional portion having an M-shape. a concave main body capable of containing a content therein and having an opening, an annularly flanged portion formed at the opening in an upper end of the concave main body, and a rib-shaped thermal fusion portion (40, 40B) formed over a whole circumference of a top surface of the flanged portion configured to be thermally fused to the film-shaped lid material for closing the opening, wherein the thermal fusion portion (40, 40B) is provided with first and second opening portions that are approximately V-shaped such that they project from the opening side toward an outer periphery of the flanged portion in a plan view, wherein each of the opening portions has an end portion located at the outer periphery side and a pair of end portions located adjacent to the opening and is adapted to allow the lid material to be easily separated or removed from the opening portion beginning by the end portion located at the outer periphery side toward the end portions located adjacent the opening, when an edge portion of the lid material is grasp and lifted by hand; a vapor discharge portion that is approximately V-shaped such that it projects from the outer periphery side toward the opening side in a plan view, wherein the vapor discharge portion has an end portion located at the opening side and is adapted to allow automatically peeling of the lid material from the end portion, when the inner pressure of the container increases due to heating; and an annular portion formed along an annular reference line, which is similar to a shape of an inner periphery of the opening, except for the first and second opening portions and the vapor discharge portion, a vapor discharge portion that is approximately V-shaped such that it projects from the outer periphery side toward the opening side in a plan view, wherein the vapor discharge portion has an end portion located at the opening side and is adapted to allow automatically peeling of the lid material from the end portion, when the inner pressure of the container increases due to heating; and an annular portion formed along an annular reference line, which is similar to a shape of an inner periphery of the opening, except for the first and second opening portions and the vapor discharge portion, wherein a pair of end portions of the vapor discharge portion located at the outer periphery side is located closer to the outer periphery than the reference line in a cross-and-width direction of the flanged portion, and wherein each of the pair of end portions is connected through an inclined portion to an end portion of the annular portion located at both sides of the vapor discharged portion; wherein the annular portion is disposed at a location less than 50% of a width of the flanged portion from the opening; characterized in that, the V-shaped first and second opening portions are formed adjacent to either side of the V-shaped vapor discharge portion as to form a multifunctional portion having an M-shape.