Recent progress of highly sensitive magnetmeter utilizing high Tc dc superconducting quantum interference device (SQUID) is reviewed briefly. Performance parameters of the SQUID magnetometer, such as field resolution, dynamic response and usability in unshielded environment, are focused on. Relationship between these performance parameters and SQUID characteristics are discussed quantitatively, and key factors which dominate each performance are clarified. With this result, design principle to obtain high performance SQUID magnetometer operating at T77K is shown. Present status on the performance of the magnetometer is discussed by comparing experimental results with theoretical predictions. Issues to much improve the performance of the high Tc SQUID magnetometer are also discussed.