Phase shift/antenna circuit having a signal line with first and third regions for engaging dielectric members and a second region that does not engage the dielectric members

An antenna device includes a plurality of phase shift circuits to which distributed signals are respectively input and a plurality of antenna elements to which signals output from the respective phase shift circuits are input. At least one of the plurality of phase shift circuits has a signal line in which a first region in which paired dielectric members are disposed, a second region in which no paired dielectric members is disposed and a third region in which paired dielectric members are disposed are provided in this order along a propagation direction of a signal. Moreover, a characteristic impedance of the first region in a state where the paired dielectric members are not disposed and a characteristic impedance of the third region in a state where the paired dielectric members are not disposed are higher than a characteristic impedance of the second region.