A random mat contains reinforcing fibers having an average fiber length of 3 to 100 mm and a thermoplastic resin, the reinforcing fiber contains reinforcing fiber bundle (A) defined as the bundle composed of the reinforcing fibers of a critical number of single fiber (defined by the following formula (1)) or more, an average thickness of the reinforcing fiber bundles (A) is 100 μm or less, and the number (n) of the reinforcing fiber bundles (A) per unit weight (g) of the reinforcing fibers satisfies the following formula (I): Critical number of single fiber=600/D (1) (wherein D is the average fiber diameter (μm) of the reinforcing fiber), and 0.65×104/L