To provide a pneumatic studless tire which exhibits high gripping performance on ice even if it is used for a large passenger car.

At least one rib 5 extending in a tire circumferential direction is formed in a tread surface, a number of thin slits 4 in a tire width direction is formed in the rib 5, the density of the thin slit 4 that defines as a B/A ratio is 0.15 /mm or more in which B is the sum total length of the slit 4 that projected on a surface which is perpendicular to the tire circumferential direction and A is the surface area of the rib 5, and also a W/S ratio is 2.40 kg/cm2 or below in which W is a load and S is the actual grounding contact area when this tire is assembled to a normal rim, an air pressure of 200 KPa is filled into the tire, and 70% load W of load ability in JATMA regulations corresponding to the air pressure thereof is loaded.