The present invention provides a grease composition which prevents frictional wear of a lubricating surface in a high load-applied state or in a state in which sliding motion is generated and is durable for a long time, a method of manufacturing capable of easily determining an addition ratio of an extreme-pressure agent of the grease composition, and a rolling bearing in which the grease composition is enclosed. A grease composition is composed by adding a thickener and an extreme-pressure agent containing sulfur in a molecular structure thereof to base oil. The extreme-pressure agent is added to the base oil so that a product of an amount (mgS/g) of active sulfur contained in the extreme-pressure agent and an addition amount (wt %) of the extreme-pressure agent with respect to an entire amount of the grease composition is in a range of 3 to 13.