The miniature specimens made from Sn-3.0Ag-0.5Cu (SAC) solder tend to show larger variation in the tensile strength than the ordinary size specimen. We assumed that the distribution morphology of the primary tin crystal in the specimen affected the strength of the specimen and investigated the relationship between the morphology and the strength. Then, we found that primary tin crystals whose longitudinal direction made 0-10° and 80-90° to the loading direction were frequently observed in the high-strength specimen, while those whose direction was 30-40° were frequent in the low-strength specimen. In this study, we conducted nanoindentation tests to investigate the deformation characteristics of the primary tin crystal and the eutectic structure in a miniature SAC solder specimen which could be useful information for discussing the direction dependency mentioned above. The result shows that the tin crystal has larger elastoplastic compliance than the eutectic structure, while the eutectic structure has larger creep compliance than the tin crystal.