TSUBAME is a university-built small satellite mission to measure polarization of hard X-ray photons (30-100 keV) from Gamma-ray bursts (GRBs) using azimuthal angle anisotropy of Compton-scattered photons. Polarimetry in the hard X-ray and soft γ-ray band plays a crucial role in the understanding of high energy emission mechanisms and the distribution of magnetic fields and radiation fields. TSUBAME has two instruments: the Wide-field Bust Monitor (WBM) and the Hard X-ray Compton Polarimeter (HXCP). The WBM determines on board the direction of the burst occurrence with an accuracy of 10 degrees, then using a high speed attitude control device, the HXCP is pointed to the GRB within 10 seconds after the burst occurrence to promptly detect polarized X-ray photons from the GRB. We present a TSUBAME mission overview, results of a Monte Carlo simulation of the X-ray polarization measurement and the plans for the future of this mission.