An object detection device (200, 201, 202, 203, 204) for a vehicle, comprising: a transmission unit configured to transmit a first transmission wave; and a reception unit configured to receive a first reception wave as the first transmission wave that is reflected by and returned from an object; a signal processing unit configured to sample a first processing target signal according to the first reception wave and to acquire a difference signal based on a difference between a value of the first processing target signal for at least one sample according to the first reception wave received at a certain detection timing, and an average value of values of the first processing target signal for a plurality of samples according to the first reception wave received in at least one of a first period and a second period of a predetermined time length that exist before and after the detection timing; a threshold setting unit configured to set a threshold which is a comparison target with the value of the difference signal, based on variation in the values of the first processing target signal for the plurality of samples; and a detection unit configured to detect information about the object at the detection timing based on a comparison result between the value of the difference signal and the threshold, wherein the transmission unit is configured to transmit a second transmission wave before transmitting the first transmission wave, the reception unit is configured to receive a second reception wave as the second transmission wave reflected by and returned from a road surface as the object before receiving the first reception wave, characterised in that the object detection device (200, 201, 202, 203, 204) further comprises a setting value acquisition unit configured to estimate a shape of the road surface based on information about a second processing target signal according to the second reception wave and to acquire a setting value according to the shape of the road surface based on the estimation result, and in that the signal processing unit is configured to acquire the difference signal based on a difference between the value of the first processing target signal for the at least one sample according to the first reception wave received at the detection timing and a larger one of the average value of the values of the first processing target signal for the plurality of samples according to the first reception wave received in at least one of the first period and the second period and the setting value. a transmission unit configured to transmit a first transmission wave; and a reception unit configured to receive a first reception wave as the first transmission wave that is reflected by and returned from an object; a signal processing unit configured to sample a first processing target signal according to the first reception wave and to acquire a difference signal based on a difference between a value of the first processing target signal for at least one sample according to the first reception wave received at a certain detection timing, and an average value of values of the first processing target signal for a plurality of samples according to the first reception wave received in at least one of a first period and a second period of a predetermined time length that exist before and after the detection timing; a threshold setting unit configured to set a threshold which is a comparison target with the value of the difference signal, based on variation in the values of the first processing target signal for the plurality of samples; and a detection unit configured to detect information about the object at the detection timing based on a comparison result between the value of the difference signal and the threshold, wherein the transmission unit is configured to transmit a second transmission wave before transmitting the first transmission wave, the reception unit is configured to receive a second reception wave as the second transmission wave reflected by and returned from a road surface as the object before receiving the first reception wave, characterised in that the object detection device (200, 201, 202, 203, 204) further comprises a setting value acquisition unit configured to estimate a shape of the road surface based on information about a second processing target signal according to the second reception wave and to acquire a setting value according to the shape of the road surface based on the estimation result, and in that the signal processing unit is configured to acquire the difference signal based on a difference between the value of the first processing target signal for the at least one sample according to the first reception wave received at the detection timing and a larger one of the average value of the values of the first processing target signal for the plurality of samples according to the first reception wave received in at least one of the first period and the second period and the setting value.