A foil type flexible pressure sensor based on piezoelectric of highly C-axis oriented aluminum nitelide (AlN) thin film deposited on an aluminum foil substrate was developed. The sensor is composed of two AlN thin films and three aluminum foils as electrodes which detect the electric charge generated by pressure acting on the AlN film. The developed sensor having excellent flexibility can fit any curved surface like skin of human beings. Directly or indirectly, pulse wave of human beings can be detected precisely by using the developed sensor.