A planar electrochemical probe includes a probe body laminated together from a plurality of solid electrolyte layers and having integrated into the probe body a gas measurement chamber which is connected to the measurement gas via a diffusion hole. The diffusion hole has a depth that extends beyond the gas measurement chamber into a solid electrolyte layer adjoining the gas measurement chamber. The manufacture of the planar electrochemical probe includes making the diffusion hole in the probe body after the electrolyte layers have been laminated together and before the layers are sintered.