The gamma-ray irradiation effects of lead sulphide photoconductive cell have been obtained experimentally. The gamma-ray source used was 10000 curie Cobalt-60,and total irradiation dose was 10^7 roentgen ～ 10^8 roentgen. The irradiation was carried out at room temperature. The results obtained are summarized as follows : (1) Coloring of the cell vessel due to the gamma-ray irradiation does not deteriorate the characteristics of the lead sulphide photoconductive cell as a near infrared detector to any appreciable degree. (2) Decrease in dark impedance of the cell due to the gamma-ray irradiation shows only a slight recovery. (3) Value of the activation energy is changed by the gamma-ray irradiation. (4) Dark current is increased, photocurrent is decreased and time constant is also decreased. Increase in dark current is due to the decrease in dark impedance of the cell, and shows little recovery. The cause of the decrease in photocurrent and time constant may be the formation of current carrier recombination centers created by the gamma-ray irradiation. (5) Current noise is increased by the gamma-ray irradiation, but recovers almost completely. Photocurrent and time constant also recover almost completely. (6) The time needed for the complete recovery of the cell photoelectric characteristics seems to be proportional to the irradiation dose. (7) From the results obtained above, it may by concluded that the lead sulphide photoconductive cell is not damaged so easily by the gamma-ray irradiation dose which was used in this experiment.