PROBLEM TO BE SOLVED: To provide a load measuring device in which the getting in/out of bed of a person in a bed can accurately be determined by measuring a body weight of the person accurately, and to provide a load offset value setting method that is necessary for measuring the body weight of the person accurately.SOLUTION: A bed 10 includes: load sensors 1-4 a variation calculating unit 46 for calculating variation in a first predetermined time of load values S1-S4 detected by the load sensors 1-4 a comparing unit 52 for comparing a first average value being an average value in the first predetermined time of the load values S1-S4 with a pre-stored load offset value, and comparing the variation with a pre-set reference variation and a load offset value setting unit 54 for setting a second average value as a new load offset value, the second average value that is an average value of the load values S1-S4 detected newly in a second predetermined time when the first average value is smaller than the load offset value and the variation is smaller than a variation threshold value.
