We report a portable respiration sensor for the analysis of respiration rates, patterns, and phases during exercise. A SiO2 nanoparticle thin film on a flexible substrate is used as a sensor chip (4.1 mm × 5 mm in area of electrodes) to detect respiration. Response and recovery time of the sensor chip are 0.7 and 1.7 s against human respiration. Even when it is covered with water, the response quickly recovers within 1 s after removal of the water. At 5 cm away from a face, a portable respiration sensor can track respiration rates up to 1.7 Hz at rest. The sensor also monitors respiration patterns and phases during exercise noninvasively. The fast-response and portable respiration sensor is usable as a healthcare device.