We present results of ^ { 12 } CO ( J = 2 - 1 ) observations toward four massive star-forming galaxies at z \sim 1.4 with the Nobeyama 45 m radio telescope .
The galaxies are detected with Spitzer /MIPS in 24 \mu \mathrm { m } , Herschel /SPIRE in 250 \mu \mathrm { m } , and 350 \mu \mathrm { m } and they mostly reside in the main sequence .
Their gas-phase metallicities derived with N2 method by using the H \alpha and [ NII ] \lambda 6584 emission lines are near the solar value .
CO lines are detected toward three galaxies .
The molecular gas masses obtained are ( 9.6 - 35 ) \times 10 ^ { 10 } ~ { } M _ { \odot } by adopting the Galactic CO-to-H _ { 2 } conversion factor and the CO ( 2-1 ) /CO ( 1-0 ) flux ratio of 3 .
The dust masses derived with the modified blackbody model ( assuming the dust temperature of 35 K and the emissivity index of 1.5 ) are ( 2.4 - 5.4 ) \times 10 ^ { 8 } ~ { } M _ { \odot } .
The resulting gas-to-dust ratios ( not accounting for HI mass ) at z \sim 1.4 are 220-1450 , which are several times larger than those in local star-forming galaxies .
A dependence of the gas-to-dust ratio on the far-infrared luminosity density is not clearly seen .