The present invention provides a polylactic acid film or sheet having tear strength so as not to break or tear during, for example, production or processing of the film or sheet or winding thereof into a roll, and causing neither melt nor deformation at high temperatures more than 100° C. In the polylactic acid film or sheet according to the present invention, the tear strength is not less than 100 N/mm when the film or sheet is torn at least in a flow direction (MD), a rate of dimensional change due to heating is not more than ±3% in the flow direction (MD) and a transverse direction (TD), and a rate of dimensional change due to loaded heating is not more than ±3% in the flow direction (MD).