Abstract: An anaerobic incubator providing for a consistently anaerobic and constant-temperature environment within an incubation jar for culture of root canal contents which comprises an incubator body, an open-top incubation jar disposed in said incubator body and comprising an outer cylindrical casing made of aluminum and, as fitted intimately therein, an inner cylindrical casing made of stainless steel, a planar heater disposed in intimate contact with the exterior surface of said outer cylindrical casing, and a temperature sensor mounted in the wall of said outer cylindrical casing. The anaerobic incubator of the invention does not require a time-consuming procedure particularly for changing water, is free from aging of heater and temperature sensor performances, and provides for improved responsiveness and controllability of the incubation jar.