The invention relates to a balancing shaft unit for piston machines, in particular internal combustion engines, for installation in a housing with non-divided bearing seats. Said shaft unit consists of at least one balancing shaft, which is configured as one piece with its balancing weight or weights. To allow the shaft unit to be installed in a non-divided housing without any restrictions being placed on its bearing, at least one bearing of the balancing shaft is formed by a narrowing of the balancing shaft that acts as a bearing journal and by a sub-divided bearing ring that is fixed to the housing, whose external diameter is greater than the external diameter of the balancing weight or weights.