To provide a boiler system that is hardly decreased in a drying degree of steam supplied from a boiler even if a demand load repeatedly varies within a predetermined range and so on.

A boiler system 1 includes: a boiler group 2 including a plurality of boilers 20 capable of burning at a plurality of stepped combustion positions including a base combustion position (M), a high combustion position (H), and a low combustion position (L); and a control section 4 which controls the combustion state of the boiler group 2 according to a demand load. When one boiler 20 in the boiler group 2 is changed in a combustion position between the base combustion position (M) and the high combustion position (H) as many time as specified within a predetermined time, the control section 4 holds the boiler 20 having been changed in the combustion position at the high combustion position (H), and changes the combustion position of a boiler positioned at the base combustion position (M) in the boiler group 2 between the base combustion position (M) and the low combustion position (L) to control the combustion state of the boiler group 2.