A liquid level detector includes a casing, a float, a magnet body, and a switch mechanism. The casing includes a tube section. The float is displaced upward or downward along a gravity direction. The magnet body is held by the float. The switch mechanism is accommodated in the tube section and is switched between an on-state and an off-state. The casing includes a first casing part and a second casing part. The first casing part includes the tube section, a first locking section that is formed radially outward of the tube section, and a first guide section that is formed at a tip of the tube section in an extending direction. The second casing part includes a second locking section and a second guide section.