Provided is a breathable structure, in which: a luer lock cap (1) is made of synthetic resin having a low melting point, including a through-hole (11) to be covered with a breathable film (2) the breathable film (2) is a two-layered film made of synthetic resin having breathability, in which a second film (22) having a low melting point adheres to a porous first film (21) having water repellency an auxiliary film body (3) is a two-layered film made of synthetic resin with an outer shape larger than an outer shape of the breathable film (2), in which a fourth film (32) having a melting point higher than a melting point of a third film (31) having a low melting point adheres to the third film (31) the breathable film (2) is connected to the auxiliary film body (3) with the second film (22) being heat-laminated to the third film (31) so that the breathable film (2) does not extend beyond the auxiliary film body (3) and the auxiliary film body (3) is connected to the luer cap lock (1) with an outer edge portion of the third film (31) being heat-laminated to the luer cap lock (1).
