A damper apparatus for being provided at a midpoint of an ink flow channel that connects an ink tank having ink stored therein and a printer head, said damper apparatus being adapted to open and close the ink flow channel in an ink jet printer that has a printer head configured to discharge ink on a printing medium and a carriage configured to move reciprocally along a predetermined scanning direction, said damper apparatus comprising: a housing having a valve chamber communicating with the ink flow channel in the interior thereof and reciprocally moving integrally with the carriage; characterized in that said valve chamber comprises: an inlet-side valve chamber and an exit-side valve chamber (311 b) divided by a partitioning portion the upper portion of which is opened; an inlet port formed in the inlet-side valve chamber (311 a) at one end portion of the housing and communicable to the ink flow channel (71 a) on the side of the ink tank; an outlet port formed in the exit-side valve chamber (311 b) at the other end portion of the housing and communicable to the ink flow channel (71 b) on the side of the printer head; and a valve body stored in each of said inlet-side valve chamber and exit-side valve chamber (311 b) so as to be relatively movable in the corresponding valve chambers (311 a and 311b), and a conical-shaped seating surface (315, 316) provided in each of said inlet-side valve chamber and exit-side valve chamber with corresponding shoulders (317, 318) provided at a boundary between said seating surfaces and a bottom surface, each seating surfaces having an inner diameter decreasing gradually toward the respective inlet and outlet ports (313, 314); such that one of the valve bodies is movable relatively to a position for closing selectively the inlet port and the other thereof for closing selectively the outlet port according to the direction of action of the inertial force upon reception of the inertial force in association with the acceleration and deceleration to close the ink flow channel when the carriage is accelerated or decelerated, and one of the valve bodies is movable relatively to a position for opening selectively the inlet port and the other thereof for opening selectively the outlet port under its own weight to open the ink flow channel when the carriage is not accelerated and decelerated. a housing having a valve chamber communicating with the ink flow channel in the interior thereof and reciprocally moving integrally with the carriage; characterized in that said valve chamber comprises: an inlet-side valve chamber and an exit-side valve chamber (311 b) divided by a partitioning portion the upper portion of which is opened; an inlet port formed in the inlet-side valve chamber (311 a) at one end portion of the housing and communicable to the ink flow channel (71 a) on the side of the ink tank; an outlet port formed in the exit-side valve chamber (311 b) at the other end portion of the housing and communicable to the ink flow channel (71 b) on the side of the printer head; and a valve body stored in each of said inlet-side valve chamber and exit-side valve chamber (311 b) so as to be relatively movable in the corresponding valve chambers (311 a and 311b), and a conical-shaped seating surface (315, 316) provided in each of said inlet-side valve chamber and exit-side valve chamber with corresponding shoulders (317, 318) provided at a boundary between said seating surfaces and a bottom surface, each seating surfaces having an inner diameter decreasing gradually toward the respective inlet and outlet ports (313, 314); such that one of the valve bodies is movable relatively to a position for closing selectively the inlet port and the other thereof for closing selectively the outlet port according to the direction of action of the inertial force upon reception of the inertial force in association with the acceleration and deceleration to close the ink flow channel when the carriage is accelerated or decelerated, and one of the valve bodies is movable relatively to a position for opening selectively the inlet port and the other thereof for opening selectively the outlet port under its own weight to open the ink flow channel when the carriage is not accelerated and decelerated.