We report a microfluidic chip that is capable of measuring volume changes in single cells in real-time. Single eukaryotic cells were immobilized in the sensing area and changes in volume in response to hypotonic challenges and drugs were measured using the electrical impedance method. Experiments on MDCK cells showed that the maximum swelling and the time course of swelling vary between individual cells following hypotonic stimulation. The microfluidic chip allows, rapid and convenient change of solutions, enabling detailed studies of various drugs and chemicals that may play important role in cell physiology at the single cell level.