Tensile strength of a tape layer in the lengthwise direction is selected to be higher than adhesive force of the tape layer to optical fiber cores.Further, position limiting portions 111 by which the positions of a plurality of optical fibers 120 can be limited are formed in a flexible film 110 for tape core assembly which film is used for integrating the plurality of optical fibers 120 as a tape.Further, a ribbon-like optical fiber core assembly 301 according to the invention including a plurality of optical fiber cores 302 arranged planarly at designated intervals, an adhesive layer 305 disposed so as to surround the optical fiber cores 302, and films 304a and 304b integrated with the optical fiber cores 302 by the adhesive layer 305.