SOURCE

var Main = {
    methods: {
      tableSpanMethod(i) {
        if (i.columnIndex === 0) {
          return [1, 2]
        } else if (i.columnIndex === 1) {
          return [0, 0]
        }
      }
    },
    data () {
      return {
        records:[
          {
            label: 'label'
          },
          {
            label: 'label------------------------'
          }
        ]
      };
    }
  }
var Ctor = Vue.extend(Main)
new Ctor().$mount('#app')

<script src="//unpkg.com/vue/dist/vue.js"></script>
<script src="//unpkg.com/element-ui/lib/index.js"></script>
<div id="app">
<template>
    <el-table :data="records" :span-method="tableSpanMethod">
        <el-table-column label="c1" prop='label' show-overflow-tooltip>
          
        </el-table-column>
        <el-table-column label="c2" prop='label'>
          
        </el-table-column>
        <el-table-column label="c3" prop='label'>
          
        </el-table-column>
        <el-table-column label="c4" prop='label'>
          
        </el-table-column>
        <el-table-column label="c5" prop='label'>
          
        </el-table-column>
    </el-table>
</template>
</div>

@import url("//unpkg.com/element-ui/lib/theme-chalk/index.css");