A resin vial cap to be attached to a mouth portion of a vial to fix a stopper fitted into the mouth portion so that the stopper may not come off the mouth portion, the vial cap comprising: a cap main body; and a cover, the cap main body comprising: a top face portion formed at an upper end of a tubular portion; an upper opening formed at a center of the top face portion and penetrating the top face portion; and a plurality of pin-receiving holes formed at the top face portion and penetrating the top face portion, and the cover covering the upper opening of the cap main body and comprising: a plate-shaped cover main body; and a plurality of fixing pins protruding downward from a lower face of the cover main body, wherein: the pin-receiving holes of the cap main body and the fixing pins of the cover are paired and each pin-receiving hole and the respective fixing pin paired with said pin-receiving hole are formed in complementary shapes; and the plurality of fixing pins of the cover are accommodated in the plurality of pin-receiving holes of the cap main body, and the cap main body and the cover are joined with the pin-receiving holes and the fixing pins engaged, wherein: the cap main body is formed with a first resin; the fixing pins are formed with a second resin; and the first resin is a resin that does not melt when the second resin in a molten state is brought into contact with the first resin. a cap main body; and a cover, the cap main body comprising: a top face portion formed at an upper end of a tubular portion; an upper opening formed at a center of the top face portion and penetrating the top face portion; and a plurality of pin-receiving holes formed at the top face portion and penetrating the top face portion, and a top face portion formed at an upper end of a tubular portion; an upper opening formed at a center of the top face portion and penetrating the top face portion; and a plurality of pin-receiving holes formed at the top face portion and penetrating the top face portion, and the cover covering the upper opening of the cap main body and comprising: a plate-shaped cover main body; and a plurality of fixing pins protruding downward from a lower face of the cover main body, wherein: the pin-receiving holes of the cap main body and the fixing pins of the cover are paired and each pin-receiving hole and the respective fixing pin paired with said pin-receiving hole are formed in complementary shapes; and the plurality of fixing pins of the cover are accommodated in the plurality of pin-receiving holes of the cap main body, and the cap main body and the cover are joined with the pin-receiving holes and the fixing pins engaged, wherein: the cap main body is formed with a first resin; the fixing pins are formed with a second resin; and the first resin is a resin that does not melt when the second resin in a molten state is brought into contact with the first resin. a plate-shaped cover main body; and a plurality of fixing pins protruding downward from a lower face of the cover main body, wherein: the pin-receiving holes of the cap main body and the fixing pins of the cover are paired and each pin-receiving hole and the respective fixing pin paired with said pin-receiving hole are formed in complementary shapes; and the plurality of fixing pins of the cover are accommodated in the plurality of pin-receiving holes of the cap main body, and the cap main body and the cover are joined with the pin-receiving holes and the fixing pins engaged, wherein: the cap main body is formed with a first resin; the fixing pins are formed with a second resin; and the first resin is a resin that does not melt when the second resin in a molten state is brought into contact with the first resin. the pin-receiving holes of the cap main body and the fixing pins of the cover are paired and each pin-receiving hole and the respective fixing pin paired with said pin-receiving hole are formed in complementary shapes; and the plurality of fixing pins of the cover are accommodated in the plurality of pin-receiving holes of the cap main body, and the cap main body and the cover are joined with the pin-receiving holes and the fixing pins engaged, wherein: the cap main body is formed with a first resin; the fixing pins are formed with a second resin; and the first resin is a resin that does not melt when the second resin in a molten state is brought into contact with the first resin. the cap main body is formed with a first resin; the fixing pins are formed with a second resin; and the first resin is a resin that does not melt when the second resin in a molten state is brought into contact with the first resin.