A water jet laser processing machine which guides a laser beam with a water column and which machines a workpiece by irradiating the workpiece with the laser beam, the processing machine comprising: a nozzle for spraying the water column, the nozzle being configured so as to be capable of introducing the laser beam into the water column, a pump for supplying pressurized water to the nozzle, a pressure sensor, connected between the pump and the nozzle, for detecting pressure of water supplied from the pump to the nozzle, the processing machine being characterised by: a storage unit storing a threshold for determining a decline in the pressure of the water supplied from the pump to the nozzle, and a relationship between the pressure of the water supplied from the pump to the nozzle and a length of a laminar flow layer of the water column, and a determination unit configured to determine whether or not the pressure detected by the pressure sensor has declined based on the pressure detected by the pressure sensor and the threshold stored in the storage unit, to thereby determine whether or not the nozzle has damage, and wherein the determination unit is further configured, when it is determined that the nozzle has damage, to calculate the length of the laminar flow layer based on the pressure detected by the pressure sensor and the relationship stored in the storage unit, and determine whether or not the length of the laminar flow layer is greater than an intended machining depth, wherein the length of the laminar flow layer means the length of the portion of the water column where the streamline has a regular shape. a nozzle for spraying the water column, the nozzle being configured so as to be capable of introducing the laser beam into the water column, a pump for supplying pressurized water to the nozzle, a pressure sensor, connected between the pump and the nozzle, for detecting pressure of water supplied from the pump to the nozzle, the processing machine being characterised by: a storage unit storing a threshold for determining a decline in the pressure of the water supplied from the pump to the nozzle, and a relationship between the pressure of the water supplied from the pump to the nozzle and a length of a laminar flow layer of the water column, and a determination unit configured to determine whether or not the pressure detected by the pressure sensor has declined based on the pressure detected by the pressure sensor and the threshold stored in the storage unit, to thereby determine whether or not the nozzle has damage, and wherein the determination unit is further configured, when it is determined that the nozzle has damage, to calculate the length of the laminar flow layer based on the pressure detected by the pressure sensor and the relationship stored in the storage unit, and determine whether or not the length of the laminar flow layer is greater than an intended machining depth, wherein the length of the laminar flow layer means the length of the portion of the water column where the streamline has a regular shape. a storage unit storing a threshold for determining a decline in the pressure of the water supplied from the pump to the nozzle, and a relationship between the pressure of the water supplied from the pump to the nozzle and a length of a laminar flow layer of the water column, and a determination unit configured to determine whether or not the pressure detected by the pressure sensor has declined based on the pressure detected by the pressure sensor and the threshold stored in the storage unit, to thereby determine whether or not the nozzle has damage, and wherein the determination unit is further configured, when it is determined that the nozzle has damage, to calculate the length of the laminar flow layer based on the pressure detected by the pressure sensor and the relationship stored in the storage unit, and determine whether or not the length of the laminar flow layer is greater than an intended machining depth, wherein the length of the laminar flow layer means the length of the portion of the water column where the streamline has a regular shape.