A phosphate-selective molecularly imprinted polymer was prepared using 1-allyl-2-thiourea as a functional monomer, and a method of sensing for phosphate was suggested using an ion-sensitive field-effect transistor (ISFET) or pH meter as a transducer. The phosphate-selective polymer bound to phosphate selectively, and the ion concentration change or the pH shift in the analyte solutions after incubation with the imprinted polymer were measured in these systems. In using ISFET electrode, concentration of phosphate from 10 to 40 mu M could be measured selectively.