アブストラクト：
We present the rest-frame optical sizes of massive quiescent galaxies at z ∼ 4 measured at K′-band with IRCS and AO188 on Subaru telescope. We observed the five galaxies suppressed star formation at z~4 selected from photometric redshift in SXDS field. Their mean size is reff = 0.8 kpc with M* ∼ 10^11 M_sun. Their size evolution follows ∝ (1 + z)−2.0±0.1, steeper than that of star forming galaxies. Our study is near the limit of the current facilities but JWST and LUVOIR will extend the redshift baseline and give us deeper insights into the evolution of massive galaxies.