We report a continuous-wave yellow laser at 578nm obtained by doubly resonant intracavity sum-frequency mixing of thin disk Yb:YAG laser and Nd:YAG laser with a LBO nonlinear crystal. Single-wavelength laser operation at 578nm by using a silica etalon as a wavelength selector and dual-wavelength operation at 578nm and 582nm are obtained with maximum output powers of 100mW and 136mW, respectively. The single wavelength operating power stability value in 30min was ~4.7%, which was improved ∼21.6%, compared with that of dual-wavelength operation.