An autosampler comprising: a sample collection part configured to collect a sample by sucking the sample from a sample container; a sample loop for holding a sample collected by the sample collection part; and an injection valve (14,14a,14b,14c) that has a plurality of connection ports and a rotor having channels (X,Y,Z) that make the connection ports communicate with each other, the injection valve is configured to switch a communication state between each of the connection ports by rotation of the rotor, the plurality of connection ports includes a pump port, a column port, a first loop port (A,D), and a second loop port (A,D), the pump port is connected to a liquid delivery channel having a liquid delivery pump (6a,6b) that feeds a mobile phase, the column port is connected to an analysis channel leading to an analysis column, the first loop port connected to one end of the sample loop, the second loop port connected to the other end of the sample loop, wherein the plurality of connection ports and the channels of the rotor are provided in such a way that the injection valve is configured to be switched from a sample filling state to an intermediate state, and from the intermediate state to a sample injection state by rotation of the rotor, the sample filling state is a state in which the pump port and the column port communicate with each other while the first loop port and the second loop port do not communicate with any of the pump port and the column port, the intermediate state is a state in which the pump port and the column port communicate with each other while the first loop port communicates with the pump port and the column port, and the second loop port is closed so that an inner pressure of the sample loop raises, the sample injection state is a state in which the pump port communicates with a connection port of one of the first loop port and the second loop port while the column port communicates with a connection port of the other one of the first loop port and the second loop port. a sample collection part configured to collect a sample by sucking the sample from a sample container; a sample loop for holding a sample collected by the sample collection part; and an injection valve (14,14a,14b,14c) that has a plurality of connection ports and a rotor having channels (X,Y,Z) that make the connection ports communicate with each other, the injection valve is configured to switch a communication state between each of the connection ports by rotation of the rotor, the plurality of connection ports includes a pump port, a column port, a first loop port (A,D), and a second loop port (A,D), the pump port is connected to a liquid delivery channel having a liquid delivery pump (6a,6b) that feeds a mobile phase, the column port is connected to an analysis channel leading to an analysis column, the first loop port connected to one end of the sample loop, the second loop port connected to the other end of the sample loop, wherein the plurality of connection ports and the channels of the rotor are provided in such a way that the injection valve is configured to be switched from a sample filling state to an intermediate state, and from the intermediate state to a sample injection state by rotation of the rotor, the sample filling state is a state in which the pump port and the column port communicate with each other while the first loop port and the second loop port do not communicate with any of the pump port and the column port, the intermediate state is a state in which the pump port and the column port communicate with each other while the first loop port communicates with the pump port and the column port, and the second loop port is closed so that an inner pressure of the sample loop raises, the sample injection state is a state in which the pump port communicates with a connection port of one of the first loop port and the second loop port while the column port communicates with a connection port of the other one of the first loop port and the second loop port.