A pipe joint comprising: a joint main body that is formed in a tubular shape, at one end of which an insertion aperture into which a pipe body is to be inserted is structured, and in which a seal portion that seals a gap between the joint main body and an outer periphery of the pipe body is provided; and an inner periphery support member that is formed in a tubular shape, that structures an insertion cavity for the pipe body between the inner periphery support member and an inner periphery of the joint main body, that supports the pipe body from an inner periphery side thereof, wherein the inner periphery support member is coupled to the joint main body at a coupling portion formed at a proximal side relative to the insertion cavity, and in which air vent holes are formed at the coupling portion side relative to the seal portion in a tube axis direction of the inner periphery support member, characterised in that (i) the joint main body includes a tubular main body portion, and an engaging protrusion portion is formed at an inner periphery side of the tubular main body portion, the engaging protrusion portion protruding in a radial direction towards the inner side of the tubular main body portion; (ii) an engaging portion and a projection portion are formed at the inner periphery support member, the engaging portion protruding to a radial direction outer side at one end side of the inner periphery support member; (iii) the inner periphery support member is coupled to the tubular main body portion by the engaging portion engaging with the engaging protrusion portion, to form the coupling portion, and (iv) the inner periphery support member comprises a low stiffness portion (36, 36A, 38) with a lower stiffness than other portions of the inner periphery support member, at the insertion aperture side relative to the coupling portion. a joint main body that is formed in a tubular shape, at one end of which an insertion aperture into which a pipe body is to be inserted is structured, and in which a seal portion that seals a gap between the joint main body and an outer periphery of the pipe body is provided; and an inner periphery support member that is formed in a tubular shape, that structures an insertion cavity for the pipe body between the inner periphery support member and an inner periphery of the joint main body, that supports the pipe body from an inner periphery side thereof, wherein the inner periphery support member is coupled to the joint main body at a coupling portion formed at a proximal side relative to the insertion cavity, and in which air vent holes are formed at the coupling portion side relative to the seal portion in a tube axis direction of the inner periphery support member, characterised in that (i) the joint main body includes a tubular main body portion, and an engaging protrusion portion is formed at an inner periphery side of the tubular main body portion, the engaging protrusion portion protruding in a radial direction towards the inner side of the tubular main body portion; (ii) an engaging portion and a projection portion are formed at the inner periphery support member, the engaging portion protruding to a radial direction outer side at one end side of the inner periphery support member; (iii) the inner periphery support member is coupled to the tubular main body portion by the engaging portion engaging with the engaging protrusion portion, to form the coupling portion, and (iv) the inner periphery support member comprises a low stiffness portion (36, 36A, 38) with a lower stiffness than other portions of the inner periphery support member, at the insertion aperture side relative to the coupling portion. (i) the joint main body includes a tubular main body portion, and an engaging protrusion portion is formed at an inner periphery side of the tubular main body portion, the engaging protrusion portion protruding in a radial direction towards the inner side of the tubular main body portion; (ii) an engaging portion and a projection portion are formed at the inner periphery support member, the engaging portion protruding to a radial direction outer side at one end side of the inner periphery support member; (iii) the inner periphery support member is coupled to the tubular main body portion by the engaging portion engaging with the engaging protrusion portion, to form the coupling portion, and (iv) the inner periphery support member comprises a low stiffness portion (36, 36A, 38) with a lower stiffness than other portions of the inner periphery support member, at the insertion aperture side relative to the coupling portion.