Students have difficulties in understanding addition and subtraction of numbers. These difficulties need to be anticipated in order to find ways to reduce them. This research aims to develop the learning designs for addition and subtraction of two-digit numbers using the Realistic Mathematics Education (RME) approach. The snakes and ladders game was used as the learning media, while the language of arrows was used as the context of learning. Using educational design research, this study involved a total of 29 first graders of one of the elementary schools in Bandung City, Indonesia. The sample in this study was selected using purposive sampling. The data were collected through tests and observations. The results of this research indicated that the learning designs had a positive impact on the students' understanding of the addition and subtraction of two-digit numbers. The students' average score after learning the addition and subtraction of two-digit numbers was 70.62. The principles of Realistic Mathematics Education (RME) are the key to student success in understanding mathematical concepts. This research could be used as a reference for developing mathematics learning designs using the RME approach in elementary schools.