A metal naphthalocyanine derivative and process for producing said derivative which is represented by the following formula (I): ##STR1## wherein M represents germanium or tin; L and L' each independently represent a halogen, a hydroxyl group, an alkyl group, an alkoxy group or a siloxy group of the formula R.sub.1 R.sub.2 R.sub.3 SiO-- (wherein R.sub.1, R.sub.2 and R.sub.3 each independently represent a hydrogen atom, an alkyl group, an alkoxy group or an aryl group).
