A silicate phosphor comprising manganese as an activator, a trivalent element and a pentavalent element, wherein said trivalent element is at least one element selected from the group consisting of boron and indium, said pentavalent element is at least one element selected from the group consisting of arsenic, antimony and bismuth, the content of the trivalent element is from I × 10 -4 to 2 x 10- 2 gram-atom/mol, the content of the pentavalent element is not more than 3 × 10 -3 gram-atom/mol, and the molar ratio of the trivalent element to the pentavalent element (trivalent element/pentavalent element) is at least 1.5.