Cyclic thermal tests were performed on tungsten using the 120 keV Neutral Beam Test Stand at IPP, Nagoya University. A maximum heat flux of 8.8 kW/cm2 was first applied for 56.7 ms to large samples for a total of 5 cycles. Many surface microcracks were observed after two thermal shocks, but only a few active cracks grew further in a direction almost perpendicular to the heated surface with an average growth rate of about 0.2 mm/cycle. Thermal shocks of 50.4 ms were next applied with an average heat flux of 8.2 kW/cm2 for a total of 23 cycles. Active cracks grew in the plane lying about 3 mm below the heated surface. No visible cracks were produced in one of the four samples, but cracking occurred after cutting the sample into four identical blocks. The thermal shock cracking was restricted in the region where grain growth had occurred.