Slip detecting tactile sensors are essential to achieve a human-like gripping motion with a robot hand. In previous researches, we have proposed flexible, thin and lightweight slip sensor utilizing characteristics of pressure conductive rubber. However, It was hard for this sensor to distinguish between the object slip and the normal force change. Therefore, we consider the separative method using high frequency elements generated by object slipping. In this paper, we design the information processing method and developed the sensor detecting both contact and initial slip in high sensitivity and a simple composition.