Abstract: There is provided a wettability tester using a test material in a molten state, including: a chamber; a vacuum exhaust section exhausting the chamber; a gas supply section supplying a predetermined gas into the chamber; a sample stage disposed in the chamber; and an observation section observing morphological change associated with a temperature distribution in the test material tapped onto the sample stage, wherein the vacuum exhaust section and the gas supply section establish a vacuum atmosphere, an inert gas atmosphere, a reducing atmosphere or an air atmosphere in the chamber. It is preferable to include: a melting section disposed above the sample stage and transforming the test material into a molten state; and a tapping control section causing the test material transformed into a molten state by the melting section to be tapped.