The microstructure of a copper bowl excavated from an Edo-period grave in Mukaiyama Ruins in Nara prefecture has been investigated. The sample was subjected to optical microscopy, scanning electron microscopy, electron probe microanalysis and X-ray diffraction analysis to obtain information about the microstructure of both the base metal and the corroded layers. The bowl was made of copper containing 0.9% lead. Annealing twins were observed in the α-Cu phase, which establishes that the bowl was forged and annealed. The corroded layers were composed mainly of cuprite, malachite and copper phosphate. It is thought that the copper phosphate acted as an inhibitor to corrosion.%遺跡から出土した金属製晶のような考古遺物は，文化財保護の観点から破壊分析することを認められない場合が多い．そのため，蛍光Ⅹ線による成分分析にとどまることが多く~(1-5)），表面が腐食層で覆われている埋蔵文化財の本当の成分を知ることは難しい．まして，金属組織観察が認められることは稀であり，製造方法や熱処理の有無については，形状などから推し測ることが多い．ところが，復元することが困難なものや，本体から分断され，復元修復に使えないような破片であれば，破壊分析が認められる場合がある．
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