The present invention provides a process for producing a methylene disulfonate compound in a simple manner at low cost.The present invention provides a process for producing a methylene disulfonate compound represented by General Formula (2) comprising: reacting, in the presence of a dehydrating agent, a formaldehyde compound with a sulfonic acid compound represented by General Formula (1): wherein R1 and R2 are independently a hydrogen atom or a C1-4 alkyl group whose hydrogen atom may be substituted with halogen atom; n is an integer from 1 to 4; and when n is an integer from 2 to 4, n R1s and n R2s may be the same or different: wherein, R1, R2, and n are the same as those described above for General Formula (1).