In a method of producing a needle-mounted outer cylinder of the present invention, a melt-bond process of melting and bonding a proximal portion (31) of a needle tube (3) to an outer cylinder (2) is performed in a state in which the needle tube (3) is inserted into a needle insertion hole (41) of the outer cylinder (2) and in a state in which the outer cylinder (2) is erect. The melt-bond process is performed by imparting energy to the needle tube (3) at a portion thereof positioned at a side distal from a proximal end of the needle insertion hole (41) and from a proximal end of the needle tube (3) to allow the needle tube (3) to generate heat so that resin positioned at a heat generation portion and forming an inner surface of the needle insertion hole (41) is melted and thereafter by flowing the melted resin downward inside the needle insertion hole (41) to thereby fill a gap between an outer surface of the proximal portion of the needle tube (3) and the needle insertion hole (41).
