Provided is a handheld addition and subtraction trainer which is designed for kids to improve ability in addition and subtraction and in which a process of presenting an addition and subtraction question with random numbers on a display panel, a process of checking whether a user's answer is correct or not, and a process of presenting a next addition and subtraction question are repeatedly performed. Further, the handheld addition and subtraction trainer has a clock for measuring a user's ability in addition and subtraction by counting the number of correct answers and by measuring a time taken for finding an answer. The handheld addition and subtraction trainer includes: a random number generator which generates a random number used for an addition and subtraction practice; a display panel which displays questions for the addition and subtraction practice, and shows a number that is inputted through the number input element; a power terminal which connects a battery for supplying power; a practice type selector which selects a type of the addition and subtraction practice; a controller which controls a process of the addition and subtraction practice; and a mode selector which selects a clock mode, a timer mode, or a correct answer checking mode. The random number generator generates a random number by using a counter that cyclically counts an address number and a number, a counter output unit that outputs a current value of the counter in response to an interrupt signal, and an interrupt signal generator that generates the interrupt signal. The handheld addition and subtraction trainer includes a timer function and a clock function for measuring a time taken for practicing addition and subtraction, and a function for checking a correct answer. Accordingly, an addition and subtraction question is presented by repeatedly generating the random number so that numbers used in the addition and subtraction question is unpredictable. In addition, since timer and clock functions are provided to measure a time taken for a user to make an answer, the handheld addition and subtraction trainer can help for kids to enhance their ability in addition and subtraction in an effective manner.