In this letter, we propose a new class of phase shifter which can provide different constant phase shifts at two bands for the first time. The prescribed phase shifts AΦ ₁ (f ₁ ) and AΦ ₂ (f ₂ ) and frequency ratio (n = f ₂ /f ₁ ) of the two bands can be obtained by the developed dual-band phase-shifting line on C-section. Meanwhile, the dual-band phase-slope alignment is first realized by virtue of the two groups of coupled resonators, resulting to independently control the phase slopes at two separated bands as required. The closed-form equations and design charts are further given. For verification, a prototype dual-band phase shifter operating at 3.0 and 5.4 GHz (n = 1.8) is designed, fabricated, and tested. The measured results show the proposed phase shifter exactly achieves prescribed constant phase shifts of 90° ± 2.3° over 2.76-3.31 GHz (18%) and 180° ± 2.7° over 4.97-5.80 GHz (15%). Both the simulation and measured results are recorded with good agreement.