A heat source device which houses a plurality of heat source side components (201, 5, 202, 203, 204) and a blower, the heat source device comprising: a blower chamber housing at least the blower; a first mechanical chamber housing a first member of the heat source side components (201, 5, 202, 203, 204); a second mechanical chamber housing a second member of the heat source side components (201, 5, 202, 203, 204); a third mechanical chamber housing a connecting member (206, 211) connecting the first member and the second member to each other; a first wall portion serving as a partition between the blower chamber and the first mechanical chamber; a second wall portion serving as a partition between the blower chamber and the second mechanical chamber; and a third wall portion serving as a partition between the blower chamber and the third mechanical chamber, wherein the first mechanical chamber and the second mechanical chamber being arranged to sandwich the blower chamber in a first direction orthogonal to a rotation axis of the blower, the third mechanical chamber being arranged between the first mechanical chamber and the second mechanical chamber in the first direction, and arranged alongside the blower in a second direction orthogonal to each of the rotation axis and the first direction, the blower chamber includes an inlet through which air is taken in from outside of the blower chamber to inside of the blower chamber, an outlet through which the air is blown out from inside of the blower chamber to outside of the blower chamber, and a bell mouth arranged to connect to the outlet, the third wall portion includes a windward portion located on the inlet side relative to the bell mouth in a third direction in which the rotation axis extends, and the windward portion includes a windward end (90b, 91b) located on the inlet side in the third direction, and a leeward portion located on the outlet side relative to the windward end, when seen from the second direction, both ends of the windward end in the first direction are arranged to protrude in the third direction relative to a central portion of the windward end in the first direction. a blower chamber housing at least the blower; a first mechanical chamber housing a first member of the heat source side components (201, 5, 202, 203, 204); a second mechanical chamber housing a second member of the heat source side components (201, 5, 202, 203, 204); a third mechanical chamber housing a connecting member (206, 211) connecting the first member and the second member to each other; a first wall portion serving as a partition between the blower chamber and the first mechanical chamber; a second wall portion serving as a partition between the blower chamber and the second mechanical chamber; and a third wall portion serving as a partition between the blower chamber and the third mechanical chamber, wherein the first mechanical chamber and the second mechanical chamber being arranged to sandwich the blower chamber in a first direction orthogonal to a rotation axis of the blower, the third mechanical chamber being arranged between the first mechanical chamber and the second mechanical chamber in the first direction, and arranged alongside the blower in a second direction orthogonal to each of the rotation axis and the first direction, the blower chamber includes an inlet through which air is taken in from outside of the blower chamber to inside of the blower chamber, an outlet through which the air is blown out from inside of the blower chamber to outside of the blower chamber, and a bell mouth arranged to connect to the outlet, the third wall portion includes a windward portion located on the inlet side relative to the bell mouth in a third direction in which the rotation axis extends, and the windward portion includes a windward end (90b, 91b) located on the inlet side in the third direction, and a leeward portion located on the outlet side relative to the windward end, when seen from the second direction, both ends of the windward end in the first direction are arranged to protrude in the third direction relative to a central portion of the windward end in the first direction.