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Traditional planar electrodes for single-particle impedance measurement have difficulty in trapping and positioning particles. This paper proposes a microfluidic device for single-particle trapping and impedance measurement with a microcavity configuration. A carbon dioxide (CO2) laser technique was used to fabricate the microcavity structure, which can capture 15 µm diameter particles without requiring additional trapping structures. The measurement electrodes on both sides of the microcavity were fabricated using electroplating and deposition techniques. The advantages of the microcavity structure and electrodes are discussed. The bottom electrode spreads into the microcavity to increase measurement sensitivity and shrink the exit aperture to around 10 µm for particle trapping. The experimental results show that the device successfully captured particles and distinguished the impedance of a particle from that of phosphate-buffered saline solution.