To enhance performance by performing soot blowing of primary and secondary elements individually depending on the extent of contamination thereof and using a spray medium effectively so that a large diameter nozzle having an effective depth can be employed.

The soot blower comprises primary and secondary nozzle headers 32a, 32b fixed to the outside of a hood 7b on the secondary air outlet side reciprocally in the substantially radial direction of primary and secondary elements 3a, 3b and supplied with a spray medium 42, primary and secondary nozzle headers 31a, 31b arranged at a required interval in the longitudinal direction thereof and blowing the spray medium 42 to the primary and secondary elements 3a, 3b, and primary and secondary nozzle header drive mechanisms 35a, 35b interlocked with rotation of primary and secondary air outlet side hoods 7a, 7b to reciprocate the primary and secondary nozzle headers 32a, 32b by a required amount at a time in the direction substantially parallel with the radial direction of the primary and secondary elements 3a, 3b.