Provided is a method of determining a mobility state of a specific target. The method of determining a mobility state of a specific target by using a particle filter having particles defined as N independent random variables, the method comprising: calculating a current speed of the specific target, and calculating a value relating to a cumulative probability at which the specific target has the current speed, repeating a particle update process of updating a value of each particle by a number of times according to a predetermined rule, and calculating an average value of values that the N particles updated have, and determining a mobility state of the specific target based on the average value, wherein a weigh is calculated to use for updating the value of the particle by using the cumulative probability.