A sample injection device is used to inject a sample into a chromatograph and includes a flow vial, a sampling needle and one or more than one sample dissolution devices. A sample is supplied to the flow vial. The sample that has been supplied to the flow vial is collected by the sampling needle and injected into the chromatograph. At least one of ultrasonic waves, an electric field and a magnetic field is used, so that dissolution of a sample to be injected into the chromatograph is promoted by one or more than one sample dissolution devices.