Between a feed roll (2,41) feeding an entangled multifilament yarn (Y) to a measuring zone of degree of entanglement and a yarn-forwarding roll (4,43) forwarding the yarn (Y) out of the measuring zone are disposed a first tension roll (16a,44a) with a weight (17a) attached thereto, a pulley (3,42) connected to a rotation meter (8) and supported free to rotate, and a second tension roll (16b,44b) with a weight (17b) attached thereto. A needle (5,47) capable of piercing the yarn (Y) is provided between the pulley (3,42) and either one of the first and the second tension rolls (16a,44a,16b,44b). Under the state wherein the needle (5,47) pierces the yarn (Y), an auxiliary weight (14a,14b,51a,51b) is added to the first or the second tension roll (16a,44a or 16b,44b), and the movement distance of the yarn (Y) from the position where the needle (5,47) pierces the yarn (Y) to the position where the point of entanglement (Yc) is engaged with the needle (5,47) is measured by detecting the amount of rotation of the pulley (3,42). Next, the auxiliary weight (14b,51b) is removed, an auxiliary weight (14a,51a) is added to the other tension roll (16b,44b or 16a,44a), and the movement distance of the yarn (Y) from the above position to the position where another point of entanglement (Yd) is engaged with the needle (5,47) is measured similarly.
The measured movement distance of the yarn (Y) corresponds to the distance between the points of entangle­ment (Yc,Yd) and gives a measure of the entanglement. By the measuring apparatus, the degree of entanglement in a yarn (Y) can be measured automatically with high accuracy without using a tension meter.