A glass powder for glass ionomer cement is disclosed, containing a glass powder for glass ionomer cement having a shape in which a major axis length is from 3 to 1,000 times a minor axis length, in a glass powder for glass ionomer cement. The glass powder for glass ionomer cement having a shape in which a major axis length is from 3 to 1,000 times a minor axis length is a fibrous glass having a minor axis length of from 0.1 to 100 &mgr;m and a major axis length of 500 &mgr;m or less, and its content is within a range of from 0.1 to 80% by weight, being enable to provide a glass ionomer cement set material having a high mechanical strength, particularly bending strength and tensile strength.