A medical instrument with attached needle of the present invention includes: a needle tube (6) having a needle tip capable of piercing a living body； and a seal member (5) composed of an elastic member and provided to hold an outer surface of the needle tube (6) in a liquid-tight manner in a condition where the needle tip (6a) capable of piercing the living body protrudes from one end and a proximal portion (6b) on a side opposite to the needle tip (6a) protrudes from the other end. The instrument also has: a liquid containing section (3) having a liquid chamber (10) capable of containing a liquid therein； and a needle seating section (2) formed at one end of the liquid containing section (3). The seal member (5) is in contact with an inner surface of the needle seating section (2) and is disposed within the needle seating section (2) in a compressed state. The proximal portion (6b) of the needle tube (6) communicates with the liquid chamber (10).
