A method for determining behavior of thyroid tumor of a subject, comprising: a first measurement step comprising measuring expression levels of at least 6 genes selected from the group consisting of AIF1L, CDH16, FAM162B, FGFR2, GJB6, KCNJ13, KIAA1467, SLC25A15, TFCP2L1, TFF3, and TMEM171 in a sample collected from thyroid lesion tissues of the subject; a second measurement step comprising measuring expression levels of at least 7 genes selected from the group consisting of C4orf10, CCDC8, CD22, FAM125A, FAM174B, FBF1, GLB1L2, LOC644613, MAP2K2, MTG1, PFKL, PTDSS2, SF3A2, SLC2A11, VILL, VSIG2, and WDR18 in the sample; a third measurement step comprising measuring expression levels of at least 7 genes selected from the group consisting of ANXA1, C13orf33, CYP1B1, FAP, FN1, IL17RD, PDLIM4, RUNX2, and TIMP1 in the sample; and determination step comprising determining whether a thyroid tumor in a subject is benign or malignant based on the results of first, second, and third measurements, wherein in the determination step, when the expression state of the genes measured in the first measurement is more than or equal to the expression state of the genes measured in the second measurement, and when the expression state of the genes measured in the first measurement is more than or equal to the expression state of the genes measured in the third measurement, the thyroid tumor of the subject is determined to be benign, when the expression state of the genes measured in the second measurement is more than the genes measured in the first measurement, and when the expression state of the genes measured in the second measurement is more than or equal to the expression state of the genes measured in the third measurement, the thyroid tumor of the subject is determined to a first malignant tumor, and when the expression state of the genes measured in the third measurement is more than the expression states of the genes measured in the first and second measurements, the thyroid tumor of the subject is determined to a second malignant tumor, wherein the first malignant tumor is a malignant tumor with poor prognosis, and the second malignant tumor is a malignant tumor with good prognosis. a first measurement step comprising measuring expression levels of at least 6 genes selected from the group consisting of AIF1L, CDH16, FAM162B, FGFR2, GJB6, KCNJ13, KIAA1467, SLC25A15, TFCP2L1, TFF3, and TMEM171 in a sample collected from thyroid lesion tissues of the subject; a second measurement step comprising measuring expression levels of at least 7 genes selected from the group consisting of C4orf10, CCDC8, CD22, FAM125A, FAM174B, FBF1, GLB1L2, LOC644613, MAP2K2, MTG1, PFKL, PTDSS2, SF3A2, SLC2A11, VILL, VSIG2, and WDR18 in the sample; a third measurement step comprising measuring expression levels of at least 7 genes selected from the group consisting of ANXA1, C13orf33, CYP1B1, FAP, FN1, IL17RD, PDLIM4, RUNX2, and TIMP1 in the sample; and determination step comprising determining whether a thyroid tumor in a subject is benign or malignant based on the results of first, second, and third measurements, wherein in the determination step, when the expression state of the genes measured in the first measurement is more than or equal to the expression state of the genes measured in the second measurement, and when the expression state of the genes measured in the first measurement is more than or equal to the expression state of the genes measured in the third measurement, the thyroid tumor of the subject is determined to be benign, when the expression state of the genes measured in the second measurement is more than the genes measured in the first measurement, and when the expression state of the genes measured in the second measurement is more than or equal to the expression state of the genes measured in the third measurement, the thyroid tumor of the subject is determined to a first malignant tumor, and when the expression state of the genes measured in the third measurement is more than the expression states of the genes measured in the first and second measurements, the thyroid tumor of the subject is determined to a second malignant tumor, wherein the first malignant tumor is a malignant tumor with poor prognosis, and the second malignant tumor is a malignant tumor with good prognosis.