Effect of ball‐mill treatment on physical properties and molecular change of maize starch granule was investigated. Ball‐mill treatment was done by rotary type mill, and species of maize starch are normal, waxy and high amylose (amylo). Running time of the treatment is 0–320 h. Starch granules loss smoothness on surface and became rough, even though their changing speed was different among the three species. But, they retained whole figure and size after 320 h treatment in the all cases. Amylase susceptivity and water absorption activity were measured. Structural change of starch components was compared among the three species with X‐ray diffraction, DSC and GPC. High Performance An‐ion Exchange Chromatography (HPAEC) pattern of debranched sample treated with ball‐mill for 320 h showed that formation of very short chain in amylopectin is little. 13C solid‐NMR spectra suggest that disruption of molecules of amylopectin and amylose with ball‐mill might occur at their glycosidic linkage. However, very slight radical was observed by Electron Spin Resonance spectroscopy (ESR) in the case of 320 h sample.