An embodiment of the invention relates to a TOF-MS capable of performing mass spectrometry of a sample at a high throughput. The TOF-MS has an acceleration part for accelerating an ion, a detector for detecting an event of arrival of the accelerated ion, and a data processing part for performing mass spectrometry of the sample, based on a time of flight of the ion. A first structure of the detector includes an MCP, a dynode, and an anode. In the first structure, the dynode is set at a potential higher than that of an output face of the MCP. The anode is disposed at an intermediate position between the MCP and the dynode or on the dynode side with respect to the intermediate position. The anode has plural apertures and is set at a potential higher than that of the dynode.