To provide a hard surface-modifying agent which can impart an anti-staining property having excellent durability against abrasion and a high temperature and high moisture environment to a hard surface.

The hard surface-modifying agent is characterized by including a perfluoropolyether phosphate (hereinafter, occasionally referred to as phosphate) obtained by reacting a diol compound represented by general formula (1) (wherein, R^f is a divalent straight chain perfluoropolyether; n and m are each independently an integer of 1 or 2) with phosphorus pentoxide in a diol compound: phosphorus pentoxide ratio of 1 mole: 0.25-0.7 mole.