A blood coagulation analyzing method according to one or more aspects may include: calculating a coagulation time based on data representing a coagulation curve of a change in an optical detection value of a blood specimen added with a reagent for starting a coagulation reaction; calculating an index value related to derivatives calculated concerning the coagulation curve represented by the data used in the calculating the coagulation time; and determining whether an early reaction error has occurred based on a comparison result obtained by comparing the index value to a predetermined threshold.