The purpose of this study was to observe and identify the phases of amalgam and to know the transformation of microstructure in the set amalgam by lapse of time. In this study, shofu spherical-D alloy was used. After trituration of amalgam alloy and mercury (Wig-L-Bug), it was filled in the stone dies. This specimens being polished and etched by usual method was observed under optical microscope using metallurgical microscope. And then X-ray diffractometer was used to analyze the phases contents and transformation of microstructure at $2{frac{1}{2}}$ hours, 15 hours, 28 hours and 2 years after being amalgamated. The following results were obtained: 1. Shofu spherical-D alloy powder was composed of ${gamma}$ phase, ${epsilon}$phase and Ag-Cu eutectic phases. 2. ${gamma}_2$ phases were appeared at $2{ heta}$ values ($32.0^{circ}$ and $43.8^{circ}$) in the amalgam which was analyzed at $2{frac{1}{2}}$ hours and 15 hours after trituration with mercury. 3. In the amalgam at 28 hours, ${gamma}_2$ phase was found at $2{ heta}$ value ($43.8^{circ}$) at 35 hour, $r_2$ phase was appeared at $2{ heta}$ value $32.0^{circ}$. 4. No ${gamma}_2$ phases were observed in the 2 years old amalgam. But ${eta}$ ($Cu_6Sn_5$) phases were found at $2{eta}$ values $29.4^{circ}$ and $42.4^{circ}$.