An end cap according to a disclosed embodiment is connected to a downstream side of a flow path of a medical liquid injection apparatus and is configured such that a priming liquid is introduced into the end cap. The end cap includes: a refraction part formed of a transparent material having a refractive index (nr) greater than 1 and including a first surface and a second surface forming an internal angle smaller than 90 degrees; and a indication part disposed to be spaced apart from the second surface. The end cap forms a passage in which the introduced priming liquid is movable, and a part of the passage is located between the second surface and the indication part.