A board work machine that includes a rotary head with multiple positions is provided for lowering nozzle holders and is able to continue operating even though it is determined that the nozzle holder cannot be lowered at one of the multiple positions. In step S1 in a Z shaft updating process, when determining based on Z shaft table that a lifting and lowering operation function is not effective and that an assigned Z shaft is not used for lifting and lowering, CPU lifts up and lowers a Z shaft that differs from the assigned Z shaft in step S11. Mounter can continue mounting work by using the Z shaft that differs from the assigned Z shaft.