1var chart = new Chart(ctx, {
2   type: 'line',
3   data: {
4      labels: ['Jan', 'Feb', 'Mar'],
5      datasets: [{
6         label: 'LINE',
7         data: [3, 2, 4],
8         backgroundColor: 'rgba(0, 119, 290, 0.2)',
9         borderColor: 'rgba(0, 119, 290, 0.6)'
10      }]
11   },
12   options: {
13      responsive: false,
14      scales: {
15         yAxes: [{
16            afterFit: function(scale) {
17               scale.width = 20  //<-- set value as you wish 
18            },
19            scaleLabel: {
20               display: true,
21               labelString: 'y-axis label',
22            }
23         }]
24      }
25   }
26});