Inner part and resin molded article

An inner part, around which an outer portion is to be arranged through integral molding, the inner part comprising:

• a main body portion made of resin;
• and
• a melt rib provided protruding outward from the main body portion,
• wherein the melt rib has a height that is greater than a thickness of the melt rib, and the melt rib includes a rising portion that has a constant thickness, and a melting portion with a thickness that gradually decreases from a distal end of the rising portion to a distal end of the melt rib, and
• the melting portion has a vertical surface and an inclined surface that is inclined with respect to the vertical surface, a thickness on the rising portion side of the melting portion is equal to the thickness direction of the rising portion, and a portion of the melting portion melts during molding of the outer portion.