A head assembly comprising: a rigid substrate including a connector and on which a power source is mounted; a plurality of heads ; a tank configured to store an ink which is to be supplied to the plurality of heads; a plurality of tubes each fluidically connecting the tank and one of the plurality of heads; a heater configured to warm the ink in the tank and in the plurality of tubes; a plurality of flexible substrates each including an end electrically connected to one of the plurality of heads; a relay substrate to which the other end of each of the plurality of flexible substrates and the connector of the rigid substrate are electrically connected; a first member defining a first space (S1) and including an airflow port configured to take an outside air thereinto; and a second member defining a second space (S2) which is arranged on one side in a first direction with respect to the first space, wherein the rigid substrate is arranged in the first space, wherein the tank, the heater, the plurality of tubes and the plurality of flexible substrates are arranged in the second space, wherein the relay substrate is arranged between the first space and the second space in the first direction, and partitions the first space and the second space from each other; wherein the relay substrate includes a first connector electrically connected to the connector of the rigid substrate, and a plurality of second connectors each of which is electrically connected to the other end of one of the plurality of flexible substrates; and wherein the first connector of the relay substrate is arranged in a first surface, of the relay substrate, defining the first space (S1) and wherein the plurality of second connectors of the relay substrate are arranged in a second surface, of the relay substrate, defining the second space. a rigid substrate including a connector and on which a power source is mounted; a plurality of heads ; a tank configured to store an ink which is to be supplied to the plurality of heads; a plurality of tubes each fluidically connecting the tank and one of the plurality of heads; a heater configured to warm the ink in the tank and in the plurality of tubes; a plurality of flexible substrates each including an end electrically connected to one of the plurality of heads; a relay substrate to which the other end of each of the plurality of flexible substrates and the connector of the rigid substrate are electrically connected; a first member defining a first space (S1) and including an airflow port configured to take an outside air thereinto; and a second member defining a second space (S2) which is arranged on one side in a first direction with respect to the first space, wherein the rigid substrate is arranged in the first space, wherein the tank, the heater, the plurality of tubes and the plurality of flexible substrates are arranged in the second space, wherein the relay substrate is arranged between the first space and the second space in the first direction, and partitions the first space and the second space from each other; wherein the relay substrate includes a first connector electrically connected to the connector of the rigid substrate, and a plurality of second connectors each of which is electrically connected to the other end of one of the plurality of flexible substrates; and wherein the first connector of the relay substrate is arranged in a first surface, of the relay substrate, defining the first space (S1) and wherein the plurality of second connectors of the relay substrate are arranged in a second surface, of the relay substrate, defining the second space. <EOS>