We have developed a high temperature superconductor (HTS) micrometer-sized dc superconducting quantum interference device (SQUID) magnetometer for high field and high temperature operation. It was fabricated from YBa2Cu3O7-δ of 92 nm in thickness with photolithography techniques to have a hole of 4×9 μm2 and 2 μm wide grain boundary Josephson junctions. Combined with a three dimensional magnetic field coil system, the modulation patterns of critical current Ic were observed for three different field directions. They were successfully used to measure the magnetic properties of a molecular ferrimagnetic microcrystal (23×17×13 μm3), [Mn2(H2O)2(CH3COO)][W(CN)8]∙2H2O. The magnetization curve was obtained in magnetic field up to 0.12 T between 30 and 70 K. This is the first to measure the anisotropy of hysteresis curve in the field above 0.1 T with an accuracy of 10-12 J T-1 (10-9 emu) with a HTS micro-SQUID magnetometer.