Provided is a new high-durability magnesia carbon brick with further improved density (reduced porosity). This magnesia carbon brick comprises a magnesia raw material and graphite and includes 8-25 mass% of graphite and 75-92 mass% of magnesia raw material in the total amount of magnesia raw material and graphite. As the particle size composition of the magnesia raw material, this magnesia carbon brick includes 35 mass% or more of magnesia raw material with a particle size of 0.075-1 mm in the total amount of magnesia raw material and graphite, and the mass ratio of magnesia raw material with a particle size of 0.075-1 mm with respect to the magnesia raw material with a particle size of less than 0.075 mm is 4.2 or more. Further, this magnesia carbon brick has an apparent porosity of 7.8% or less after three hours of reduction firing at 1400°C.
