The present disclosure relates to a wavy smoke tube structure of a boiler, which improves heat exchange efficiency of a smoke tube. The wavy smoke tube structure includes: a main body formed in a columnar shape and having a space therein; a plurality of first concave portions concavely formed along a first side portion in a longitudinal direction of the main body; a plurality of second concave portions concavely formed along a second side portion in the longitudinal direction of the main body opposite to the first side portion and each positioned between a pair of the first concave portions to face them; and a plurality of blocking grooves formed in a pair of sidewall portions provided between the first side portion and the second side portion.