A fluorescent lamp including a glass bulb, a protection layer formed on an inner surface of the glass bulb, and a phosphor layer formed on a surface of the protection layer. The surface of the protection layer that is in contact with the phosphor layer has cracks. The bulk density of the metal oxide particles in the protection layer 32 is 80% or more. The surface of the protection layer 32 has 20 to 200 cracks per millimeter in a tube axis direction. The average particle diameter of the metal oxide particles is in the range from 0.01 .mu.m to 1 .mu.m. The thickness of the protection layer is in the range from 0.5 .mu.m to 5 .mu.m.