Provided are a liquid ejection device and a maintenance method thereof which are capable of effectively removing, for example, a liquid in a gap between heads. The liquid ejection device includes: a line head which includes a plurality of heads connected to each other in a longitudinal direction and in which a liquid-repellent treatment is performed for a side surface of each head facing an adjacent head; a tube supporting member that is provided between adjacent heads on a side opposite to a liquid ejection surface of the head and supports a tube having one end inserted between the heads; and a gas supply unit that is connected to the other end of the tube and supplies gas between the heads from the one end of the tube.