A low pressure mercury vapor discharge lamp includes a bulb and a mercury-releasing metal substrate, in particular, an alloy of zinc and mercury in which the mercury-releasing metal substrate has an inside part crystallized in a plate form or in a granular form and a surface on which a mercury-rich layer is formed. The mercury-releasing metal substrate, in particular, the alloy of zinc and mercury, can be adhered firmly to the inside face of the bulb. Moreover, the low pressure mercury vapor discharge lamp can be made by putting a mercury-releasing metal substrate into a bulb; forming a mercury-rich layer on the surface of the mercury-releasing metal substrate while crystallizing the inside of the mercury-releasing metal substrate in a plate form or in a granular form by heating the bulb from the outside; and softening the mercury-releasing metal substrate to adhere it to the inside face of the bulb.