A wearable device for measuring skin deformation of the fingertip- To obtain contact force when the finger touches an object-was prototyped and experimentally evaluated. The device is attached to the fingertip and uses multiple photo-reflective sensors (PRSs) to measures the distance from the PRSs to the side surface of the fingertip. The sensors do not touch the contact surface between the fingertip and the object; as a result, the contact force is obtained without changing the user's tactile sensation. In addition, the accuracy of estimated contact force was improved by determining the posture of the fingertip by measuring the distance between the fingertip and the contact surface. Based on the prototyped device, a system for estimating three-dimensional contact force on the fingertip was implemented.