Disclosed is a polyamine sheet which is usable for DNA chips or protein chips. Also disclosed are a photoreactive polyamine used for producing such a polyamine sheet, and a photoreactive compound which can be a raw material for such a photoreactive polyamine. Specifically disclosed are a photoreactive compound having a diazirine group as a photoreactive group, a photoreactive polyamine compound produced from such a photoreactive compound and a polyamine, a polyamine sheet using such a photoreactive polyamine compound, and a method for producing such a polyamine sheet.