A container packed with a mixture of powders classified respectively into two or at least three particle-size distribution groups which are different in average particle size, the powders comprising a hydrogen absorbing alloy singly or the combination of such an alloy and a substance not absorbing hydrogen. The mixture is at least 0.03 to not greater than 0.50 in the ratio d.sub.2 /d.sub.1 wherein d.sub.1 is the average particle size of the powder having the particle-size distribution of the largest average particle size, and d.sub.2 is the average particle size of the powder having the particle-size distribution of the second largest average particle size. The weight ratio of the powder to the total weight of the powders is greater when that powder has a particle-size distribution of larger average particle size. The weight ratio of the powder having the particle-size distribution of the second largest average particle size to the powder having the particle-size distribution of the largest average particle size is at least 0.2 to not greater than 0.8.