The invention relates to a cleaning device (1) comprising at least: a holder (2), a lance (3) having a fluid distribution device (4), a drive unit (5) for a translational motion of the lance (3) in the holder (2), and a fluid conducting system (6) having a feed (7), a return (8), and flow paths (9) starting from the feed (7) to the return (8) and to the fluid distribution device (4), wherein at least one actuating means (10) is provided in order to connect the feed (7) to the return (8) or to the fluid distribution device (4) as needed. The invention further relates to a method for cleaning heating surfaces (23) of a convection section (18) of a thermal power plant (17) that comprise spaced heat exchanger pipes (21) using such a cleaning device (1).