A method of producing a needle-mounted outer cylinder involves a melt-bond process of melting and bonding a proximal portion of a needle tube to an outer cylinder in a state in which the needle tube is in a needle insertion hole of the outer cylinder and in a state in which the outer cylinder is erect. The melt-bond process is performed by imparting energy to a portion of the needle tube distal from a proximal end of the needle insertion hole and from a proximal end of the needle tube causing the needle tube to generate heat so that resin forming an inner surface of the needle insertion hole melts and thereafter by causing the melted resin to flow downward inside the needle insertion hole to thereby fill a gap between an outer surface of the proximal portion of the needle tube and the needle insertion hole.
