A heterodyne speckle interferometry for measurement of in-plane displacement is proposed. The wavelength-modulated (WM) laser beam passing through an unequal-path-length optical configuration is used as a heterodyne light source. The scattering heterodyne speckle signal is received by letting the WM heterodyne light incidents on the in-plane moving rough surface. The object displacement would be determined by the speckle interferometry theorem with the measured phase variation of the heterodyne speckle signal. The experimental results demonstrate that the measurement range is up to 10 μm and resolution is about 10 nm.