We propose a calcium measurement using a glass micro injector. A fluorescent dye is injected into a small area through the injector. Since a light fiber probe is placed closely at the injector tip, fluorescence depending on calcium concentration is locally detected through the probe. This method is minimally invasive for living preparations because a calcium indicator is injected only for a short time. Also this measurement avoids the photo-bleaching effect by injecting fresh dye. The relationship between calcium concentration and fluorescence was confirmed in experiment. The dose of dye is controlled by the current applied to the injector. We also obtained the relationship between the amount of the injected dye and the current. Calcium can be measured only in several micrometers when the current is limited up to 7.67 nA. Finally, a prototype device has been fabricated using MEMS technology. A photo-diode and an electrode of the injector were built together in this device.