A pen input device comprising: a tubular housing including a front opening and a rear opening disposed opposite to each other; an assembly accommodated in the housing and including: a pen input generating means including a pen tip disposed in the front opening, and generating a position signal and a pen pressure signal of the pen input device, a battery, a printed circuit board, PCB, disposed between the pen input generating means and the battery, and electrically connected to the pen input generating means and the battery, and a support means on which at least a part of the pen input generating means, the battery, and the PCB are disposed; at least one conductive member electrically connecting the PCB and the battery; a buffer means disposed in the rear opening; and a polymer (1010, 1020) filled in an inner space of the housing; the pen input device being further characterized by: a temperature sensor disposed on the PCB, wherein the support means includes a support plate extended in a direction toward the rear opening from the front opening of the housing, and includes a first partition, a second partition, and a third partition which are protruded from the support plate and sequentially spaced in the direction, the pen input generating means is combined with the first partition, the PCB is disposed between the first partition and the second partition, and the battery is disposed between the second partition and the third partition, a stepped structure is formed on an inner surface of the housing between the third partition and the buffer means to prevent the buffer means from moving toward the third partition, the at least one conductive member is disposed to penetrate an opening formed in the second partition, the pen input device includes a fourth partition disposed on a first surface of the PCB between the first partition and the second partition, the polymer (1010, 1020) includes: a first polymer disposed at least between the first partition and the fourth partition, and a second polymer disposed at least between the fourth partition and the battery, the temperature sensor is covered by the second polymer, and the temperature sensor detects a temperature of the battery through the second polymer, the second polymer including a heat transfer material. a tubular housing including a front opening and a rear opening disposed opposite to each other; an assembly accommodated in the housing and including: a pen input generating means including a pen tip disposed in the front opening, and generating a position signal and a pen pressure signal of the pen input device, a battery, a printed circuit board, PCB, disposed between the pen input generating means and the battery, and electrically connected to the pen input generating means and the battery, and a support means on which at least a part of the pen input generating means, the battery, and the PCB are disposed; a pen input generating means including a pen tip disposed in the front opening, and generating a position signal and a pen pressure signal of the pen input device, a battery, a printed circuit board, PCB, disposed between the pen input generating means and the battery, and electrically connected to the pen input generating means and the battery, and a support means on which at least a part of the pen input generating means, the battery, and the PCB are disposed; at least one conductive member electrically connecting the PCB and the battery; a buffer means disposed in the rear opening; and a polymer (1010, 1020) filled in an inner space of the housing; a temperature sensor disposed on the PCB, wherein the support means includes a support plate extended in a direction toward the rear opening from the front opening of the housing, and includes a first partition, a second partition, and a third partition which are protruded from the support plate and sequentially spaced in the direction, the pen input generating means is combined with the first partition, the PCB is disposed between the first partition and the second partition, and the battery is disposed between the second partition and the third partition, a stepped structure is formed on an inner surface of the housing between the third partition and the buffer means to prevent the buffer means from moving toward the third partition, the at least one conductive member is disposed to penetrate an opening formed in the second partition, the pen input device includes a fourth partition disposed on a first surface of the PCB between the first partition and the second partition, the polymer (1010, 1020) includes: a first polymer disposed at least between the first partition and the fourth partition, and a second polymer disposed at least between the fourth partition and the battery, a first polymer disposed at least between the first partition and the fourth partition, and a second polymer disposed at least between the fourth partition and the battery, the temperature sensor is covered by the second polymer, and the temperature sensor detects a temperature of the battery through the second polymer, the second polymer including a heat transfer material.