A laser machining device comprising: a control device, a laser source, an attenuation optical system, a dichroic mirror, lenses (25, 26), a heat radiation sensor, a power meter, a stage, a total reflection mirror, and a reference work irradiation object, wherein the laser source is configured to emit a laser beam; the optical attenuator is configured to irradiate, with the laser beam emitted from the laser source, a machining object or the irradiation object; the heat radiation sensor is configured to measure heat radiation of the irradiation object or the machining object irradiated with the laser beam by the optical attenuator; the power meter is configured to measure power of the laser beam on the irradiation object irradiated with the laser beam by the optical attenuator; and the laser power control device comprises a processor and a storage, wherein the processor is configured to: create relational data having a measurement value of the heat radiation of the irradiation object from the heat radiation sensor in association with a power value of the laser beam on the irradiation object from the power meter, estimate power of the laser beam on the machining object based on a measurement value of the heat radiation sensor and the relational data stored in the storage, and adjust power of the laser beam irradiated on the machining object based on an estimation result, and wherein the storage is configured to store the relational data. a control device, a laser source, an attenuation optical system, a dichroic mirror, lenses (25, 26), a heat radiation sensor, a power meter, a stage, a total reflection mirror, and a reference work irradiation object, wherein the laser source is configured to emit a laser beam; the optical attenuator is configured to irradiate, with the laser beam emitted from the laser source, a machining object or the irradiation object; the heat radiation sensor is configured to measure heat radiation of the irradiation object or the machining object irradiated with the laser beam by the optical attenuator; the power meter is configured to measure power of the laser beam on the irradiation object irradiated with the laser beam by the optical attenuator; and the laser power control device comprises a processor and a storage, wherein the processor is configured to: create relational data having a measurement value of the heat radiation of the irradiation object from the heat radiation sensor in association with a power value of the laser beam on the irradiation object from the power meter, estimate power of the laser beam on the machining object based on a measurement value of the heat radiation sensor and the relational data stored in the storage, and adjust power of the laser beam irradiated on the machining object based on an estimation result, and wherein the storage is configured to store the relational data. create relational data having a measurement value of the heat radiation of the irradiation object from the heat radiation sensor in association with a power value of the laser beam on the irradiation object from the power meter, estimate power of the laser beam on the machining object based on a measurement value of the heat radiation sensor and the relational data stored in the storage, and adjust power of the laser beam irradiated on the machining object based on an estimation result, and wherein the storage is configured to store the relational data.