A method for high speed in vitro screening a library selected from the group consisting of cDNA library and nucleic acid aptamer library comprising steps of: (i) preparing both of a positive spherical shaped structure or a negative spherical shaped structure, wherein a target molecule is immobilized on the positive spherical shaped structure but it is not immobilized on the negative spherical shaped structure; (ii) forming the positive spherical shaped conjugate or the negative spherical shaped conjugate by respectively binding a target detecting molecule capable of binding to the target molecule, which is selected from either the library having the size equal to or more than 10 10 to form the positive spherical shaped structure or the negative spherical shaped structure; (iii) separating the positive and negative spherical shaped conjugates by using a fluorescence cell sorter; (iv) amplifying a nucleic acid bound to the target molecule on a surface of the separated positive or the separated negative spherical shaped conjugates by using PCR; (v) repeating the steps (i) to (iv) by using all of the double strand DNA obtained in the amplification step within 5 times; and (vi) analyzing the respective PCR product obtained from the positive spherical shaped conjugates and from the negative spherical shaped conjugates, wherein the target detecting molecule is either a nucleic acid-linker conjugate obtained from the cDNA library by using cDNA display method; or a nucleic acid sequence obtained from the nucleic acid-linker conjugate; and wherein, if applies, the target detecting molecule is obtained by using cDNA display method comprising the steps of: (a) preparing a desirable mRNA; (b) binding the desirable mRNA to the linker by using 3-cyanovinylcarbazole to obtain mRNA-linker conjugate; (c) forming mRNA-linker-protein conjugate by translating the mRNA-linker conjugate; and (d) conducting reverse transcription of the mRNA-linker-protein conjugate to obtain mRNA/cDNA-linker-protein conjugate. (i) preparing both of a positive spherical shaped structure or a negative spherical shaped structure, wherein a target molecule is immobilized on the positive spherical shaped structure but it is not immobilized on the negative spherical shaped structure; (ii) forming the positive spherical shaped conjugate or the negative spherical shaped conjugate by respectively binding a target detecting molecule capable of binding to the target molecule, which is selected from either the library having the size equal to or more than 10 10 to form the positive spherical shaped structure or the negative spherical shaped structure; (iii) separating the positive and negative spherical shaped conjugates by using a fluorescence cell sorter; (iv) amplifying a nucleic acid bound to the target molecule on a surface of the separated positive or the separated negative spherical shaped conjugates by using PCR; (v) repeating the steps (i) to (iv) by using all of the double strand DNA obtained in the amplification step within 5 times; and (vi) analyzing the respective PCR product obtained from the positive spherical shaped conjugates and from the negative spherical shaped conjugates, wherein the target detecting molecule is either a nucleic acid-linker conjugate obtained from the cDNA library by using cDNA display method; or a nucleic acid sequence obtained from the nucleic acid-linker conjugate; and wherein, if applies, the target detecting molecule is obtained by using cDNA display method comprising the steps of: (a) preparing a desirable mRNA; (b) binding the desirable mRNA to the linker by using 3-cyanovinylcarbazole to obtain mRNA-linker conjugate; (c) forming mRNA-linker-protein conjugate by translating the mRNA-linker conjugate; and (d) conducting reverse transcription of the mRNA-linker-protein conjugate to obtain mRNA/cDNA-linker-protein conjugate. either a nucleic acid-linker conjugate obtained from the cDNA library by using cDNA display method; or a nucleic acid sequence obtained from the nucleic acid-linker conjugate; and wherein, if applies, the target detecting molecule is obtained by using cDNA display method comprising the steps of: (a) preparing a desirable mRNA; (b) binding the desirable mRNA to the linker by using 3-cyanovinylcarbazole to obtain mRNA-linker conjugate; (c) forming mRNA-linker-protein conjugate by translating the mRNA-linker conjugate; and (d) conducting reverse transcription of the mRNA-linker-protein conjugate to obtain mRNA/cDNA-linker-protein conjugate. (a) preparing a desirable mRNA; (b) binding the desirable mRNA to the linker by using 3-cyanovinylcarbazole to obtain mRNA-linker conjugate; (c) forming mRNA-linker-protein conjugate by translating the mRNA-linker conjugate; and (d) conducting reverse transcription of the mRNA-linker-protein conjugate to obtain mRNA/cDNA-linker-protein conjugate.