A nickel-metal hydride secondary battery includes: a plurality of power generating elements each having a negative plate containing hydrogen absorbing alloy; a battery case provided with partition walls and a plurality of compartments arranged adjacently on both sides of each partition wall, each of the compartments accommodating each power generating element, and the compartments allowing gas intercommunication between compartments through communication holes formed in the partition walls; and at least one of safety valves placed on the battery case, the safety valves being less in number than the number of the compartments; wherein each of the communication holes has a hole sectional area per battery module capacity in a range 0.03 to 0.30 mm2/Ah.