An infusion apparatus comprising: an infusion set (2; 2a); and a controller, the infusion set including: a first flow path having a first connector, which is to be connected to a first container for storing a first liquid, at one end, and a downstream connector at the other end; a first open/close valve and a drip chamber provided on the first flow path; a second flow path having a second connector, which is to be connected to a second container for storing a second liquid, at one end; a second open/close valve provided on the second flow path, characterised in that the infusion set further includes: a variable valve, wherein the first open/close valve, the drip chamber, and the variable valve are provided in this order on the first flow path from the first connector side toward the downstream connector side; a droplet sensor, a first liquid surface sensor, and a second liquid surface sensor that the drip chamber is provided with in this order from an upper side toward a lower side; an air discharge tube that is in communication with a gas storing portion in the drip chamber; and an air discharge tube open/close valve that the air discharge tube is provided with; wherein the second flow path is in communication with a portion of the first flow path between the first open/close valve and the drip chamber, and the controller is configured to control the first open/close valve, the variable valve, the second open/close valve, and the air discharge tube open/close valve based on signals from the droplet sensor, the first liquid surface sensor, and the second liquid surface sensor. an infusion set (2; 2a); and a controller, the infusion set including: a first flow path having a first connector, which is to be connected to a first container for storing a first liquid, at one end, and a downstream connector at the other end; a first open/close valve and a drip chamber provided on the first flow path; a second flow path having a second connector, which is to be connected to a second container for storing a second liquid, at one end; a second open/close valve provided on the second flow path, a first flow path having a first connector, which is to be connected to a first container for storing a first liquid, at one end, and a downstream connector at the other end; a first open/close valve and a drip chamber provided on the first flow path; a second flow path having a second connector, which is to be connected to a second container for storing a second liquid, at one end; a second open/close valve provided on the second flow path, characterised in that the infusion set further includes: a variable valve, wherein the first open/close valve, the drip chamber, and the variable valve are provided in this order on the first flow path from the first connector side toward the downstream connector side; a droplet sensor, a first liquid surface sensor, and a second liquid surface sensor that the drip chamber is provided with in this order from an upper side toward a lower side; an air discharge tube that is in communication with a gas storing portion in the drip chamber; and an air discharge tube open/close valve that the air discharge tube is provided with; a variable valve, wherein the first open/close valve, the drip chamber, and the variable valve are provided in this order on the first flow path from the first connector side toward the downstream connector side; a droplet sensor, a first liquid surface sensor, and a second liquid surface sensor that the drip chamber is provided with in this order from an upper side toward a lower side; an air discharge tube that is in communication with a gas storing portion in the drip chamber; and an air discharge tube open/close valve that the air discharge tube is provided with; wherein the second flow path is in communication with a portion of the first flow path between the first open/close valve and the drip chamber, and the controller is configured to control the first open/close valve, the variable valve, the second open/close valve, and the air discharge tube open/close valve based on signals from the droplet sensor, the first liquid surface sensor, and the second liquid surface sensor.