A decorative lighting device includes: a light-emitting unit; a holding unit which includes an inner surrounding wall that has an outer wall surface, an outer surrounding wall that has a surrounding engaging surface spaced apart from the outer wall surface with a surrounding clearance, and an annular connecting wall that attaches the outer surrounding wall to the outer wall surface to form a surrounding abutment surface confronting the surrounding clearance; and a light-transmissive housing which includes an annular neck portion that terminates at an annular edge, that has inner and outer annular surfaces, and that is configured such that once the annular edge is brought to abut against the surrounding abutment surface, the outer annular surface is engaged with the surrounding engaging surface, while the inner annular surface is spaced apart from the outer wall surface to thereby cut off creepage of intruding extraneous water into the inner surrounding wall.