1. 먼저 클래스 직렬화로 만들기

using UnityEngine;
using System.Collections;
using System;

// ( 이것 때문에 하루 걸렸다 ㅠ 클래스 앞에 꼭 [Serializable] 붙이기 )

[Serializable]
public class Sm_mlevel_st_entry
{
    private string stl1;
    private string stl2;
    private string stl3;
    private string stl4;
    private string stl5;

   public Sm_mlevel_st_entry(string _stl1, string _stl2, string _stl3, string _stl4, string _stl5)
   {
        this.stl1 = _stl1; //ml_level
        this.stl2 = _stl2; //ml_1
        this.stl3 = _stl3; //ml_2
        this.stl4 = _stl4; //ml_3
        this.stl5 = _stl5; //ml_4
    }

    public string getStl1()
    {
        return stl1;
    }
    public string getStl2()
    {
        return stl2;
    }
    public string getStl3()
    {
        return stl3;
    }
    public string getStl4()
    {
        return stl4;
    }
    public string getStl5()
    {
        return stl5;
    }

}

2. 저장 및 로드 함수

    public object LoadData(string file_Name)
    {
        if (File.Exists(Application.dataPath + "/Sm_data_table/" + file_Name + ".dat"))
        {
            var b = new BinaryFormatter();
            var f = File.Open(Application.dataPath + "/Sm_data_table/" + file_Name + ".dat", FileMode.Open);
            object obj = b.Deserialize(f);
            f.Close();
            return obj;
        }
        else
        {
            return null;
        }
    }

    public void SaveData( string file_Name, object tmp_list )
    {
        var b = new BinaryFormatter();
        var f = File.Create(Application.dataPath + "/Sm_data_table/" + file_Name + ".dat");
        b.Serialize(f, tmp_list);
        f.Close();
    }

3. 사용하기

        List<Sm_mlevel_st_entry> tmpList = new List<Sm_mlevel_st_entry>();

        for (int i = 0; i < 5; i++)
        {
            Sm_mlevel_st_entry entry1 = new Sm_mlevel_st_entry("1q " + i.ToString(), "2w " + i.ToString(), "3e " + i.ToString(), "4r " + i.ToString(), "5t " + i.ToString());
            tmpList.Add(entry1);
        }

        Sm_data_table.instance.SaveData("sm_mlevel_st", tmpList); // 세이브

        List<Sm_mlevel_st_entry> tmpList2 = new List<Sm_mlevel_st_entry>();

        tmpList2 = (List<Sm_mlevel_st_entry>) Sm_data_table.instance.LoadData("sm_mlevel_st"); // 로드