To provide a pump unit in which sticking of liquid is eliminated at the time of starting operation, and to provide a liquid ejector equipped with that pump unit.

When a motor M is driven to turn a drive shaft Ma anticlockwise under a second state where a third coupling member 32 is coupled with a fourth coupling member 33, the driving force is transmitted sequentially to a pinion gear PG (anticlockwise) to a second helical gear HG2 (clockwise) to the third and fourth coupling members 32 and 33 (clockwise) to a shaft 34 (clockwise) to a second coupling gear CG2 (clockwise) to a first coupling gear CG1 (anticlockwise) to a drive haft 23 (anticlockwise). Consequently, the drive gear of the gear pump GP rotates with a large torque.