A desolvation unit performs desolvation by heating after a sample solution is turned to sample mist by a nebulizer. A sample gas that contains the desolvated sample mist and a carrier gas is introduced through a sample introduction tube to a plasma torch. An addition unit for adding, to the sample introduction tube, a water-containing gas is provided. The addition unit includes a container that contains ultrapure water, a gas tube for introducing the carrier gas into the ultrapure water to cause bubbling, and a gas tube for adding the water-containing gas, to the sample introduction tube. The plasma torch generates an inductively coupled plasma under the condition that supplied power is set to a range of 550 W to 700 W. Generation of interfering molecule ions due to an element having a high ionization potential is inhibited when an element in a sample ionized by the plasma is analyzed.