In this paper, experimental study of hardness measurement process affected by a cushion between the probe and PTF (polymer thick film) pressure sensor was discussed. Hardness sensing for soft material has been one of the important problems in many fields such as foods industry and material science. One difficulty is how to measure the weak contacting force (0.1 to few N)stable with the small target deformation by low-cost force sensor such as PTF, and we found the result of the measurement stability depending on a cushion between the probe and PTF sensor. The result shows that (1) the output force value depends on the kind of cushion material (plastic, urethane, rubber, styrene elastomer, etc.), (2) the force value was affected by the sensor probe angle to the target material. This result would be useful to develop and study the hardness sensing process intending to reduce the target deformation.