A dental primer composition comprising:(A) a polymerizable monomer containing an acidic group, (B) water, (C) an aryl borate represented by the following formula (1): ##STR4## wherein R1, R2 and R3 are the same or different and each is an alkyl group, alkenyl group, alkinyl group, aryl group, aralkyl group or alkaryl group and may be substituted, R4 and R5 are the same or different and each is a h