1. An extreme ultraviolet light generation apparatus comprising: a chamber including a plasma generation region to which a target is supplied, the target being turned into plasma so that extreme ultraviolet light is generated in the chamber; a target supply part configured to supply the target to the plasma generation region by outputting the target as a droplet into the chamber; a droplet detector configured to detect the droplet traveling from the target supply part to the plasma generation region; an imaging part configured to capture an image of an imaging region containing the plasma generation region in the chamber; and a controller configured to control an imaging timing at which the imaging part captures the image of the imaging region, based on a detection timing at which the droplet detector detects the droplet, wherein the droplet is turned into plasma upon being irradiated with a laser beam in the plasma generation region, and emits plasma light containing the extreme ultraviolet light; the controller controls an irradiation timing at which the droplet is irradiated with the laser beam in the plasma generation region, based on the detection timing; the controller sets a first imaging timing to a timing just after the irradiation timing; and the imaging part captures an image of the plasma light generated in the imaging region at the first imaging timing.