PURPOSE: To vary a phase over a wide band by connecting a 90° HYB and a 0° HYB through conductor lines having the same electric length, inserting variable attenuators in the respective conductor lines, and setting the attenuation values of both attenuators so that a desired output phase shift is obtained.

CONSTITUTION: When voltages obtained at an output 16 through a path 10a extending from an input 11 to the output 16 through a variable attenuator 17 and a path 10b extending through a variable attenuator 18 are denoted as Va and Vb, the Va and Vb are 90° out of phase with each other regardless of frequency because the paths 10a and 10b are equal in electric length. Then, the composite voltage of both voltages at the output 16 is represented as Vc=Va+Vb. Those Va and Vb are controlled by the variable attenuators 17 and 18 so that Va= V0cosθ and Vb=jV0sinθ, and then Vc=V0(cosθ+jsinθ)=V0ejθ, so that the output is V0 constantly and has a phase θ. Namely, when the attenuators 17 and 18 are controlled in the relation shown by said equation, the wide band variable phase device which has the constant output voltage and shifts in phase by a specific extent is obtained.