A magnetic fluid detecting device (1) that detects magnetic fluid that has been injected into a living body has a detector (2) that detects magnetic fluid in the body when it is in contact with or adjacent to the body, an output device (3) that outputs the detection results in a prescribed output form, a controller (4) that controls the output device (3) based on the detected value inputted from the detector (2), and a power supply module (5) that supplies power to the detector (2), output device (3) and controller (4), using a battery B as the power source. The detector (2), output device (3), controller (4) and power supply module (5) are integrated to allow holding with one hand.
