PURPOSE: To form the slit portion of an aperture type fluorescent lamp in a beautiful shape by preventing the deposition of mercury on the slit portion serving as the light transmitting portion.

CONSTITUTION: A light reflecting film 7 is formed on the inside of a glass bulb 1 in a preset area in a bulb-peripheral direction except for the slit portion 9 serving for transmitting light along the tube-axial direction, a light transmitting metal oxide protecting film 10 is formed on the inside of the light reflecting film and on the inside of the light transmitting slit portion of the bulb, and in addition a fluorescent coating 8 laminated is formed on the inside of the protecting film 10 in opposition to the light reflecting film 7. As a result, the protecting film 10 formed on the inside of the bulb 1 prevents the contact of the glass 1 directly with mercury, and so no deposition of mercury occurs on the inside of the slit portion 10.