An interlacing device comprising: an interlacing portion configured to interlace a yarn and including a yarn running space in which the yarn runs; characterized in that the interlacing device further comprises: a yarn introduction device configured to introduce the yarn into the interlacing portion, and in that the interlacing portion further includes: an injection unit configured to inject air into the yarn running space; and a yarn introduction passage through which the yarn is introduced into the yarn running space, the yarn introduction passage including a first yarn passage which extends in a first direction orthogonal to a yarn running direction in the yarn running space and has a yarn insertion slot at an end on one side in the first direction, and the yarn introduction device including an insertion member which presses the yarn from the one side toward the other side in the first direction to insert the yarn into the first yarn passage through the insertion slot. an interlacing portion configured to interlace a yarn and including a yarn running space in which the yarn runs; characterized in that the interlacing device further comprises: a yarn introduction device configured to introduce the yarn into the interlacing portion, and in that the interlacing portion further includes: an injection unit configured to inject air into the yarn running space; and a yarn introduction passage through which the yarn is introduced into the yarn running space, the yarn introduction passage including a first yarn passage which extends in a first direction orthogonal to a yarn running direction in the yarn running space and has a yarn insertion slot at an end on one side in the first direction, and the yarn introduction device including an insertion member which presses the yarn from the one side toward the other side in the first direction to insert the yarn into the first yarn passage through the insertion slot. a yarn introduction device configured to introduce the yarn into the interlacing portion, and in that the interlacing portion further includes: an injection unit configured to inject air into the yarn running space; and a yarn introduction passage through which the yarn is introduced into the yarn running space, the yarn introduction passage including a first yarn passage which extends in a first direction orthogonal to a yarn running direction in the yarn running space and has a yarn insertion slot at an end on one side in the first direction, and the yarn introduction device including an insertion member which presses the yarn from the one side toward the other side in the first direction to insert the yarn into the first yarn passage through the insertion slot. an injection unit configured to inject air into the yarn running space; and a yarn introduction passage through which the yarn is introduced into the yarn running space, the yarn introduction passage including a first yarn passage which extends in a first direction orthogonal to a yarn running direction in the yarn running space and has a yarn insertion slot at an end on one side in the first direction, and the yarn introduction device including an insertion member which presses the yarn from the one side toward the other side in the first direction to insert the yarn into the first yarn passage through the insertion slot.