NOVELTY - A chemically strengthened glass is manufactured by ion exchange carried out by substituting alkali metal ion (A) of glass of glass plate surface with alkali metal ion (B) having ionic radius more than that of metal ion (A). The glass before ion exchange process contains (in %mass) silicon oxide (65-75), mixture (5-20) of sodium oxide and potassium oxide, calcium oxide (2-15), magnesium oxide (0-10) and aluminum oxide (0-5). The glass plate has surface pressure shrinkage stress of 600-900 MPa and compressive stress layer having depth of 5-20 mu m at surface.    USE - Chemically strengthened glass for cover glass used for display apparatus used for mobile telephone, smart phone, tablet personal computer and solar cell.    ADVANTAGE - The chemically strengthened glass has excellent cuttability and high residual compressive stress.    DETAILED DESCRIPTION - A chemically strengthened glass is manufactured by ion exchange method carried out by substituting alkali metal ion (A) contained in glass of glass plate surface with alkali metal ion (B) having ionic radius more than that of metal ion (A). The glass before ion exchange process is soda lime glass comprising (in %mass) silicon oxide (65-75), mixture (5-20) of sodium oxide and potassium oxide, calcium oxide (2-15), magnesium oxide (0-10) and aluminum oxide (0-5). The glass plate has surface pressure shrinkage stress of 600-900 MPa after ion exchange, and has compressive stress layer having depth of 5-20 mu m at surface. A graph (G1) is prepared by plotting ratio of content of alkali metal ion (B) with respect to total content of alkali metal ions (A,B) in vertical axis, and depth from glass surface in horizontal axis, and plot in graph is approximated by quartic curve with least square method. A graph (G2) is prepared by plotting absolute value of differential coefficient at first order differential of quartic curve in vertical axis and depth from glass surface in horizontal axis, and plot at depth of 0-5 mu m is approximated by primary straight line with least square method. The inclination of primary straight line is -4 to -0.4. An INDEPENDENT CLAIM is included for manufacture of chemically strengthened glass.