A method for analyzing metal fine particles in liquid by use of an inductive coupling plasma mass spectrometer comprising: a sample storage section for storing a sample solution to be measured; a sample introduction section having a sample nebulizer and a sample spray chamber; a torch section for ionizing the sample by forming a plasma; an interface section for taking ions from the plasma; a mass analysis section for separating ions; and a detection section for detecting the separated ions, wherein the inductive coupling plasma mass spectrometer is provided with a separately installed standard solution introduction apparatus comprising a standard solution storage unit for storing a standard solution containing a specific element in a known concentration, a syringe pump for suctioning and discharging the standard solution, and a solution introduction unit having a standard solution nebulizer and a standard solution spray chamber that are supplied with the standard solution, a standard solution introduction passage for introducing the standard solution flowing out from the standard solution spray chamber is connected to a flow passage connecting the sample introduction section to the torch section, the standard solution is directly supplied to the standard solution nebulizer at a flow rate of 3 μL/min or less to introduce the standard solution into the torch section from the solution introduction unit, wherein the standard solution signal intensity changes in a linear manner with the flow rate of the standard solution, and a standard solution sensitivity value that is a specific element weight per standard solution signal intensity count is determined based on a standard solution signal intensity obtained from a detector and a physical amount of the introduced specific element, and a particle diameter value of metal fine particles of the specific element is calculated from a sample solution signal count number of one metal fine particle of the specific element, which is obtained from the detector by introduction of the sample solution, and the standard solution sensitivity value. the inductive coupling plasma mass spectrometer is provided with a separately installed standard solution introduction apparatus comprising a standard solution storage unit for storing a standard solution containing a specific element in a known concentration, a syringe pump for suctioning and discharging the standard solution, and a solution introduction unit having a standard solution nebulizer and a standard solution spray chamber that are supplied with the standard solution, a standard solution introduction passage for introducing the standard solution flowing out from the standard solution spray chamber is connected to a flow passage connecting the sample introduction section to the torch section, the standard solution is directly supplied to the standard solution nebulizer at a flow rate of 3 μL/min or less to introduce the standard solution into the torch section from the solution introduction unit, wherein the standard solution signal intensity changes in a linear manner with the flow rate of the standard solution, and a standard solution sensitivity value that is a specific element weight per standard solution signal intensity count is determined based on a standard solution signal intensity obtained from a detector and a physical amount of the introduced specific element, and a particle diameter value of metal fine particles of the specific element is calculated from a sample solution signal count number of one metal fine particle of the specific element, which is obtained from the detector by introduction of the sample solution, and the standard solution sensitivity value.