A sensor is provided with a sensor element which outputs a signal in accordance with a detected object contained in a specimen positioned on a detection part in an element surface and with a package which accommodates the sensor element inside it and has a passage including a space positioned on the element surface. A lower surface of the passage has the element surface and a lower surface of an inflow passage extending toward the space, and a gap is positioned between the lower surface of the inflow passage and the element surface. The element surface is positioned above the lower surface of the inflow passage.