Adapter and injection fluid transfer method

An injection fluid transfer method comprising:

• preparing an adapter for transferring a predetermined injection fluid, via an injection port of an injection nozzle, to an injection device that injects the predetermined injection fluid from the injection nozzle, the adapter including a housing defining a containing portion containing the predetermined injection fluid to be transferred and a filling nozzle connected to the containing portion in the housing, an open end of the filling nozzle being set to be smaller than an inner diameter of the containing portion and larger than the injection port of the injection nozzle, the filling nozzle including a protruding portion having an annular shape and protruding from the filling nozzle toward a distal end side of the adapter, the protruding portion being formed in a manner where, when the housing is attached to the injection device, a distal end of the protruding portion comes into contact with the end surface of the injection device, of an internal space of the housing from a partial region of the containing portion connected to the filling nozzle to the open end of the filling nozzle, at least a predetermined space inside the protruding portion being formed in a manner where an inner diameter of the predetermined space decreases toward a side of the open end of the filling nozzle;
• attaching the housing to the injection device and causing a distal end of the filling nozzle to be in contact with an end surface of the injection device, in which the injection port of the injection nozzle is formed;
• pouring the predetermined injection fluid into the containing portion;
• and
• transferring the predetermined injection fluid from the containing portion to the injection device in a state where the adapter is positioned above the injection device in a vertical direction.