An asynchronous sampling frequency conversion device comprising: a storage unit configured to store input digital signals; a data specifying unit configured to specify first data and second data based on a ratio of a sampling frequency of the input digital signal to a sampling frequency of an output digital signal, the first data being sampled at a sampling timing immediately before an i th, where i is a natural number, sampling timing of the output digital signal among the input digital signals stored in the storage unit, the second data being sampled at the sampling timing immediately after the i th sampling timing of the output digital signal; and an output data value calculator configured to calculate a value of i th data of the output digital signal based on the first data and the second data specified by the data specifying unit and the ratio, characterized in that the data specifying unit is configured to specify the first data that is rounddown value in accord with a sequence of the sampling timing, and to specify the second data that is roundup value in accord with the sequence of the sampling timing, the rounddown value being obtained by rounding down a multiplication value to a natural number, the roundup value being obtained by rounding up the multiplication value to a natural number, the multiplication value being obtained by multiplying the ratio and i indicating the sequence of the sampling timing of data to be calculated by the output data value calculator; and the output data value calculator is configured to calculate the value of the i th data of the output digital signal through linear interpolation using the first data and the second data specified by the data specifying unit, the multiplication value, the rounddown value, and the roundup value. a storage unit configured to store input digital signals; a data specifying unit configured to specify first data and second data based on a ratio of a sampling frequency of the input digital signal to a sampling frequency of an output digital signal, the first data being sampled at a sampling timing immediately before an i th, where i is a natural number, sampling timing of the output digital signal among the input digital signals stored in the storage unit, the second data being sampled at the sampling timing immediately after the i th sampling timing of the output digital signal; and an output data value calculator configured to calculate a value of i th data of the output digital signal based on the first data and the second data specified by the data specifying unit and the ratio, characterized in that the data specifying unit is configured to specify the first data that is rounddown value in accord with a sequence of the sampling timing, and to specify the second data that is roundup value in accord with the sequence of the sampling timing, the rounddown value being obtained by rounding down a multiplication value to a natural number, the roundup value being obtained by rounding up the multiplication value to a natural number, the multiplication value being obtained by multiplying the ratio and i indicating the sequence of the sampling timing of data to be calculated by the output data value calculator; and the output data value calculator is configured to calculate the value of the i th data of the output digital signal through linear interpolation using the first data and the second data specified by the data specifying unit, the multiplication value, the rounddown value, and the roundup value.