Injection mold, injection molding method, and molded article

An injection mold provided with a partition member that forms a first cavity part configured to mold a first material and forms a second cavity part configured to mold a second material by moving after molding of the first material,

• wherein a portion of the first cavity part that is formed by the partition member and molds a joining part of the first material joined to the second material includes an inclined part forming part that molds a first material inclined part inclined so that a thickness of the joining part becomes thinner toward an end edge of the first material in the joining part, and a thinned-part forming part that is continuously connected to the inclined-part forming part and forms a first material thinned part of a predetermined thickness in a part of the joining part,
• the joining part has a linear part having a linear shape, and a curved part having a curved shape,
• a sum of a length of the inclined-part forming part and a length of the thinned-part forming part in a width direction of the linear part is at least equal to a predetermined value, and a sum of a length of the inclined-part forming part and a length of the thinned-part forming part in a width direction of the curved part is at least equal to the predetermined value,
• a thickness of the thinned-part forming part that molds the linear part is substantially the same as a thickness of the thinned-part forming part that molds the curved part, and
• the length of the thinned-part forming part in the width direction of the linear part is less than than the length of the thinned-part forming part in the width direction of the curved part.