The aerodynamic characteristics of thin airfoils at low Reynolds number were investigated in a Mars Wind Tunnel at Tohoku University. The lift and the drag of five airfoils (NACA 0012, 5% flat plate, 1% flat plate, 3% circular arc, 6% circular arc) were investigated by using a two-component balance system at Re=1.1×104 and Mach number about 0.2. Also, Pressure-Sensitive Paint technique was used to measure pressure distributions around the airfoils. The results obtained by the balance system show that The maximum lift to drag ratio of the 3% circular arc is the largest among the airfoils tested in this study. And the results of PSP measurement show that the lift slope becomes large where a bubble with relatively short length appears on the airfoil surface, and the thicker airfoil has longer separation bubble than the thin airfoil at the same angle of attack. Furthermore, the airfoil surface having large curvature, the range of angles of attack where the separation bubble exists becomes narrow because the appearance of a separation bubble by an increase of angle of attack is delayed.