A genotyping method and a prepared oligomicroarray as device is to determine single nucleotide polymorphism (SNP) and mutations are provided. The method uses two specific APEX-2 primers per each SNP or mutations to be determined. The same primers are used in amplification phase (primer extension and PCR with universal primer) and in the single base extension phase on an array. All SNP-containing sequences can be genotyped and amplified in one reaction tube and visualized on a microarray.