A benzylalcohol derivative of the formula: ##STR1## wherein R is hydroxy, benzyloxy, alkoxy of one to 4 carbon atoms or halogen, and Ring A is monomethoxyphenyl, dimethoxyphenyl, trimethoxyphenyl or 3,4-methylenedioxyphenyl is prepared by reducing a compound of the formula: ##STR2## wherein R' is benzyloxy, alkoxy of one to 4 carbon atoms or halogen, and Ring A is the same as defined above, and when R' is benzyloxy, if required, further subjecting the product to catalytic hydrogenation.The compounds (I) and pharmaceutically acceptable acid addition salts thereof are used as anti-diabetic agents.