A modularized structure of switch wire connection device includes an assembling support and a wire connection module. The assembling support has a first side and a second side. The first and/or the second sides are formed with assembling sections for assembling with the wire connection module. The wire connection module includes a first wire connection module and/or a second wire connection module each having a case. The case defines a chamber for receiving and enclosing electrical contact components. The case is formed with a mounting section for connecting with the assembling section of the assembling support. The wire connection module is detachably mounted on the assembling support as an integrated form. The modularized structure enables an operator to easily assemble/disassemble the components and change the switch specification between normally open mode and normally closed mode and enhance insulation effect to avoid electric arc.