A method for analyzing blood coagulation comprising: acquiring information relating to coaguability of blood based on a change generated in a complex permittivity spectrum measured in a coagulation process of the blood due to addition of a substance that activates platelets to the blood, the method comprises the following steps adding a substance that activates platelets into a blood sample to initiate a coagulation process of the blood sample; obtaining a complex permittivity spectrum in the coagulation process of the blood sample; determining a change of the measured complex permittivity spectrum with respect to that of a reference complex permittivity spectrum of the blood sample without the substance, wherein the change is the shortening width Δt of the blood coagulation time; comparing the change with a reference value set by using blood known to have normal coaguability, wherein the reference value is the shortening time Δt s of the blood coagulation time; and said acquiring information relates to coagulability of the blood sample based on the comparison, wherein whether the aggregability of the platelets is good is determined depending on whether the shortening width Δt of the blood coagulation time of the sample blood is larger or smaller than Δt s, wherein, the information includes aggregability of the platelets included in the blood sample in an inactive state, wherein each of Δt and Δt s is calculated by t 0 -t 1, wherein t 0 is the blood coagulation time indicated by the spectrum peak po, when the platelet activating agent is not added, and t 1 is the blood coagulation time indicated by the spectrum peak p 1 when the platelet activating agent is added. acquiring information relating to coaguability of blood based on a change generated in a complex permittivity spectrum measured in a coagulation process of the blood due to addition of a substance that activates platelets to the blood, the method comprises the following steps adding a substance that activates platelets into a blood sample to initiate a coagulation process of the blood sample; obtaining a complex permittivity spectrum in the coagulation process of the blood sample; determining a change of the measured complex permittivity spectrum with respect to that of a reference complex permittivity spectrum of the blood sample without the substance, wherein the change is the shortening width Δt of the blood coagulation time; comparing the change with a reference value set by using blood known to have normal coaguability, wherein the reference value is the shortening time Δt s of the blood coagulation time; and said acquiring information relates to coagulability of the blood sample based on the comparison, wherein whether the aggregability of the platelets is good is determined depending on whether the shortening width Δt of the blood coagulation time of the sample blood is larger or smaller than Δt s, wherein, the information includes aggregability of the platelets included in the blood sample in an inactive state, wherein each of Δt and Δt s is calculated by t 0 -t 1, wherein t 0 is the blood coagulation time indicated by the spectrum peak po, when the platelet activating agent is not added, and t 1 is the blood coagulation time indicated by the spectrum peak p 1 when the platelet activating agent is added.