Abstract: A pipe coupling universal joint has a first fitting portion and a second fitting portion. An edge circumference of the first or second fitting portion is separated from a reference plane by a length set to 21 to 23% of the maximum diameter length of the first or second fitting portion on the reference plane in a direction opposite to a side where a straight pipe portion is connected from the reference plane.

Abstract: Provided is a liquid pipe coupling universal joint capable of easily performing a pipe mount work even in a narrow space, remarkably reducing a piping work cost, providing a high coupling strength in a structure of the universal joint itself and excellent vibration and earthquake resistance. Disclosed is a pipe coupling universal joint (100) in which an edge circumference (12, 13) of the first or second fitting portion (3, 7) is formed in a position separated from a reference plane (T) by a length (L) set to 21 to 23% of the maximum diameter length (R1, R2) of the first or second fitting portion (3, 7) on the reference plane (T) in a direction (V) opposite to a side where the straight pipe portion (1) is connected from the reference plane (T) defined herein.