An optical time domain reflectometer includes: an OTDR measurement unit; an event detection unit that detects an event using the measurement result of the OTDR measurement unit; a display unit that displays a plurality of icons indicating events in an event display region AIV and displays information of an event, which is located in a specific region AATT of the event display region AIV, in an information display region AINF; an operation detection unit that detects a swipe operation in the event display region AIV; and an event-of-interest changing unit that scrolls the events displayed in the event display region AIV according to the swipe operation to change the display of the information display region AINF to information corresponding to the event indicated by the icon located in the specific region AATT.