...
<el-table-column 
type="index" 
label="編號"
:index="getIndex"
width="80px">
 </el-table-column>
...
<Pagination
  :total="total"
  :pageSize="pageSize"
  :currentPage="currentPage"
  @sizeChange="sizeChange"
  @currentChange="currentChange">
</Pagination>

 getIndex (index) {
  if (this.currentPage==0){
    return (this.currentPage) * this.pageSize + index + 1
  } else{
    return (this.currentPage-1) * this.pageSize + index + 1
  }
 },

sizeChange(val){
  let that = this;
  that.currentPage = 1;
  that.pageSize = val;
  that.getPageInfo(that.currentPage, val);
},

currentChange(val){
  let that = this;
  that.currentPage = val;
  that.getPageInfo(val, that.pageSize);
},

getUserList(currentPage, pageSize){
  let that = this;
  that.$axios({
   method: 'get',
   url: '***',
   params: {
    currentPage: (currentPage || that.currentPage || 1)-1,
    pageSize: pageSize || that.pageSize || 10
   },
   needInterceptors: true,
   showError: true,
   loader: true
  }).then(function(result){
   let data = result && result.data || [];
   let page = result && result.pageCont || {};
   that.total = page.totalItems || 0;
   that.tableData = data;
  })
 },