Abstract: Multipole circuit breaker comprising single-pole breaking units in the form of cases with two large side faces and having at least one movable contact which operates in conjunction with at least one stationary contact, an operating mechanism common to a set of breaking units to command opening or closing of the contacts of said units, first line-side electrical connection means, second load-side electrical connection means; the breaking units are grouped on two superposed layers, at least one layer comprising at least one pair of units, the operating mechanism comprising mechanical connecting means to simultaneously actuate the single-pole breaking units of each layer.