An analog conversion device includes an analog-to-digital (A/D) converter; a shared memory that has an A/D conversion-value storage area for storing the converted digital value and a log storage area for logging a digital value that is stored in the A/D conversion-value storage area and that can be read and accessed from a central processing unit (CPU) that controls an entire programmable controller; a logging execution unit that stores the digital value stored in the A/D conversion-value storage area in the log storage area as logging data; a fixed-number logging detection unit that monitors whether the number of the logging data to be stored in the log storage area has reached a predetermined number since the last interrupt generation request has been made; and an interrupt generation unit that makes an interrupt generation request to the CPU when the number of the logging data has reached the predetermined number.