An optical connector plug for accommodating a ferrule assembly to hold an optical fiber, comprising: a first member formed in an approximate quadrilateral cylindrical shape, having a bottom wall, side walls which stand from ends of the bottom wall respectively so that they are opposed to one another; and a second member formed in an approximate quadrilateral cylindrical shape, being assembled with the first member; the first member including an opening to insert and hold the ferrule assembly in a longitudinal direction of the first member, and having a fitting projection (2d, 2d1) formed as being extended from the side walls thereof in the longitudinal direction; the second member comprising a main portion, an elongating portion extended from the main portion, and a joining portion extended from the elongating portion, the second member having an opening formed in a longitudinal direction of the second member to insert and hold the ferrule assembly, and side walls opposing to the side walls of the first member on which the fitting projection are formed, and the side walls of the second member having a fitting recess (3e, 3e1) formed in a longitudinal direction of the side walls of the second member; the first member having the fitting projection (2d, 2d1) longitudinally projected from an end of the wall of the first opening of the first member which is jointed to the joining portion of the second member, in the longitudinal direction of the side walls of the first member; the second member having the fitting recess (3e, 3e1) provided outer side walls of the elongating portion which are formed between the main portion and the joining portion of the second member, and the fitting recess (3e, 3e1) is formed from one end of the joining portion-side of the elongating portion, in a longitudinal direction of the side walls of the second member, and the fitting recess (3e, 3e1) corresponding to the fitting projection (2d, 2d1); the first member being provided with an engagement opening at a rear portion of the fitting projection (2d, 2d1) in a longitudinal direction thereof; the joining portion of the second memberhaving an engagement projection at the front of the fitting recess(3e, 3e1) in a longitudinal direction of the second member; and the optical connector plug, wherein the engagement openings of the first member and the engagement projection of the second member being joined by engaging the fitting projection (2d, 2d1) of the first member with the fitting recess (3e, 3e1) of the second member, and by interdigitating the joining portion of the second member to the opening of the first member. a first member formed in an approximate quadrilateral cylindrical shape, having a bottom wall, side walls which stand from ends of the bottom wall respectively so that they are opposed to one another; and a second member formed in an approximate quadrilateral cylindrical shape, being assembled with the first member; the first member including an opening to insert and hold the ferrule assembly in a longitudinal direction of the first member, and having a fitting projection (2d, 2d1) formed as being extended from the side walls thereof in the longitudinal direction; the second member comprising a main portion, an elongating portion extended from the main portion, and a joining portion extended from the elongating portion, the second member having an opening formed in a longitudinal direction of the second member to insert and hold the ferrule assembly, and side walls opposing to the side walls of the first member on which the fitting projection are formed, and the side walls of the second member having a fitting recess (3e, 3e1) formed in a longitudinal direction of the side walls of the second member; the first member having the fitting projection (2d, 2d1) longitudinally projected from an end of the wall of the first opening of the first member which is jointed to the joining portion of the second member, in the longitudinal direction of the side walls of the first member; the second member having the fitting recess (3e, 3e1) provided outer side walls of the elongating portion which are formed between the main portion and the joining portion of the second member, and the fitting recess (3e, 3e1) is formed from one end of the joining portion-side of the elongating portion, in a longitudinal direction of the side walls of the second member, and the fitting recess (3e, 3e1) corresponding to the fitting projection (2d, 2d1); the first member being provided with an engagement opening at a rear portion of the fitting projection (2d, 2d1) in a longitudinal direction thereof; the joining portion of the second memberhaving an engagement projection at the front of the fitting recess(3e, 3e1) in a longitudinal direction of the second member; and the optical connector plug, wherein the engagement openings of the first member and the engagement projection of the second member being joined by engaging the fitting projection (2d, 2d1) of the first member with the fitting recess (3e, 3e1) of the second member, and by interdigitating the joining portion of the second member to the opening of the first member.