The aim of this talk is to study Riesz transform associated to the Grushin operator. Since the Grushin operator is closely related to the Hermite opertor, we use the spectral decomposition of Hermite operator. The main theorem is L^p-boundedness of Riesz transform. To prove this, we use Littlewood-Palet theory and an operator-valued Fourier multiplier theorem due to L.Weis.