A transmission line microwave apparatus includes at least one nonreciprocal transmission line part, which includes a series branch circuit equivalently including a capacitive element and a shunt branch circuit equivalently including an inductive element. The nonreciprocal transmission line part has gyrotropic characteristic by being magnetized in a magnetization direction different from the propagation direction of a microwave, and has an asymmetric structure to a plane formed by the propagation direction and the magnetization direction. The nonreciprocal transmission line part has a propagation constant and an operating frequency set in a dispersion curve that represents a relation between the propagation constant and the operating frequency so that the propagation constant in the forward direction and the propagation constant in the backward direction have nonreciprocal phase characteristics different from each other. A microwave transmission line is constituted by cascade-connecting at least one non-reciprocal transmission line part between first and second ports.