Provided is a thermoplastic resin composition that reduces uneven distribution of inorganic substance particles and is suitable for producing a formed article having excellent appearance and mechanical properties even when the thermoplastic resin is highly filled with inorganic substance powder and a formed article using this thermoplastic resin composition. Provided are an inorganic substance powder-containing thermoplastic resin composition including a thermoplastic resin and inorganic substance powder in a mass ratio of 50:50 to 10:90, in which the inorganic substance powder is calcium carbonate particles, the calcium carbonate particles include at least two groups of particles having different average particle diameters, and any of the average particle diameters of the particle groups is within a range of 0.7 μm or more and 6.0 μm or less; and a formed article using this inorganic substance powder-containing thermoplastic resin composition.