A sample injection apparatus and sample injection method capable of sufficiently reducing carry-over, having simple cleaning means for a short cleaning time period, a small influence of vibration of the cleaning means, and a small error in the amount of injected sample and preventing the durability of a sampling needle from being lowered, and a liquid chromatography apparatus having the sample injection apparatus are provided. The sample injection apparatus has a sampling vessel 14 into which a sample is supplied, a sampling needle 10 for aspirating and ejecting the sample, a cleaning part 17 into which a cleaning liquid for cleaning at least the sampling needle 10 is supplied, a sample injection part 15 for injecting the sample ejected from the sampling needle 10 into a moving liquid, and needle transfer means for transferring the sampling needle 10 among the sampling vessel 4, the cleaning part 17 and the sample injection part 15, wherein the cleaning part 17 has an ultrasonic vibrator for generating an ultrasonic wave in the cleaning liquid.